Re: [time-nuts] OP-Amps for 10MHz distribution...?
Charles P. Steinmetz wrote: Bill wrote: At what frequency do you have 1 nv per square root Hz with opamp and what opamp ? With most op-amps suitable for a 10 MHz distribution amp, the input voltage noise is specified at 100 kHz or greater. For example, the OPA653 that Bruce tested is specified for 6.1 nV/rtHz (typical) at 100kHz and the graph shows that it has a 1/f noise corner in that vicinity, with a noise density greater than 100 nV/rtHz at 10 Hz. There are op-amps that are likely suitable for 10 MHz distribution that have lower input voltage noise than the OPA653 (again, generally specified at 100 kHz or 1 MHz): AD811 (1.9); AD8007 (2.7); AD8010 (2); ADA4899 (1); EL5166 (1.7); EL5236/7 (1.5); OPA695 (1.8); THS3001 (1.6); and THS3112 (2.2). Many of these are current-feedback amps, but if you keep the resistance at the inverting input low (200 to 75 ohms, depending on the particular amp) the inverting input current noise will be lower than the noninverting input voltage noise. If the amp has sufficient output current to drive a back-terminated 50 ohm load with authority (the OPA653 is a bit marginal in this respect, IMO), there should be no problem driving such a feedback network plus the load. I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being capable of useful operation as a 10 MHz distribution amplifier -- the ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are wonderful parts, but the large signal frequency response with a 100 ohm load is less than desired for a 10 MHz distribution amplifier. Best regards, Charles Wideband current feedback opamps tend to have a non inverting input current noise floor in the 10-20pA/rtHz region. Unless the output to inverting input feedback resistor value is less than around 250 ohms or so the equivalent input noise for a gain of 2 is greater than that of an OPA653. Unfortunately the value of this resistor cannot be arbitrarily reduced without destabilising the amplifier. The AD811, AD8007, AD8010, THS3001, THS3112 current feedback amplifiers have a higher equivalent input noise floor than the OPA653 for a voltage gain of 2. For sufficiently high gain the equivalent input noise floor of these current feedback opamps will be lower than that of the OPA653. However the output phase noise floor (limited by the maximum input signal amplitude and the amplifier equivalent input noise) with such high gain amplifiers will tend to be greater than that of the OPA653 with a gain of 2. The LMH6702 current feedback amp is stable with a 237 ohm feedback resistor and has an inverting input noise current floor of 18pA/rtHz. The equivalent input noise for a voltage gain of 2 is -158dBm/Hz. The corresponding lower limit to the phase noise floor is about -174dBc/Hz A maximum output of around +13dBm in a 50 ohm load is achievable with distortion below -70dBc @ 10MHz. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Low noise voltage at the cost of noise current which is around 1000 times that of low noise JFETs. The discussion suggest that opamps contribute to the sideband phase noise of the signal. I am interested in the mechanism that adds this phase noise. It would have to be a small shift in either gain (changing Miller capacitance) or an internal capacitance in the opamp. I am new to this group and have some catching up to do. I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being capable of useful operation as a 10 MHz distribution amplifier -- the ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are wonderful parts, but the large signal frequency response with a 100 ohm load is less than desired for a 10 MHz distribution amplifier. 73 Bill wa4lav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Bill wrote: Low noise voltage at the cost of noise current which is around 1000 times that of low noise JFETs. Sure, but the noise resistance (input termination at which voltage noise and current noise contribute equally to the output noise) is still around 400 ohms -- anything lower and the input current noise is not much of a factor. For a 10 MHz distribution amp, this condition is very likely to be met. The discussion suggest that opamps contribute to the sideband phase noise of the signal. I am interested in the mechanism that adds this phase noise. It would have to be a small shift in either gain (changing Miller capacitance) or an internal capacitance in the opamp. As you suspected, the primary mechanism is usually modulation of transistor capacitances by noise. Another is general component noise. Three good references are: Walls, et al., Origin of 1/f PM and AM Noise in Bipolar Junction Transistor Amplifiers; Ferre-Pikal, et al., Guidelines for Designing BJT Amplifiers with Low 1/f AM and PM Noise; and Ascarrunz, et al., PM Noise Generated by Noisy Components. I think Bruce has these linked on his pages at Didier's (KO4BB) site (http://www.ko4bb.com/~bruce/). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
System noise is the question. If the driving impedance is low, then voltage noise is more significant than current noise. You simply can't look at the noise of the part. The key is the noise of the entire circuit. -Original Message- From: Bill Fuqua wlfuq...@uky.edu Sender: time-nuts-boun...@febo.com Date: Wed, 29 Feb 2012 10:15:21 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...? Low noise voltage at the cost of noise current which is around 1000 times that of low noise JFETs. The discussion suggest that opamps contribute to the sideband phase noise of the signal. I am interested in the mechanism that adds this phase noise. It would have to be a small shift in either gain (changing Miller capacitance) or an internal capacitance in the opamp. I am new to this group and have some catching up to do. I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being capable of useful operation as a 10 MHz distribution amplifier -- the ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are wonderful parts, but the large signal frequency response with a 100 ohm load is less than desired for a 10 MHz distribution amplifier. 73 Bill wa4lav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Hi For a variety of reasons, you are trying to match a 50 ohm line in a distribution amplifier. The simplest reason is that mismatch adds reflections and can degrade timing. You *could* use transformers or filters to transform to higher impedance, but they add phase shift. Phase shift is a problem if it changes (over time, temperature, vibration, phase of the moon...). Change in phase = change in time = signal is degraded. Ideally you are only dealing with a single frequency. In practice you have harmonics. Since filters are out, low distortion and clean signals is a desirable feature. A reasonable question is always - how good do I need to be? If you are plugging a cable into the back of your 5334 and setting the gate to 1 second - not so good. If you want to check your Hydrogen Maser to see if it's doing ok over night- you need to be very good. The difference is likely to five of magnitude. Muddying this all up is a duality between time measurement and frequency measurement. Noise power spectral density makes a lot more sense to most of us in the frequency domain. Many of our measures of stability have time worked into them. They also take place in a region where frequency is a bit awkward to use (10 micro Hz ...). It's also a region where wideband noise floor is not as big an issue as flicker noise. Lots of fun. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Fuqua Sent: Wednesday, February 29, 2012 10:15 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...? Low noise voltage at the cost of noise current which is around 1000 times that of low noise JFETs. The discussion suggest that opamps contribute to the sideband phase noise of the signal. I am interested in the mechanism that adds this phase noise. It would have to be a small shift in either gain (changing Miller capacitance) or an internal capacitance in the opamp. I am new to this group and have some catching up to do. I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being capable of useful operation as a 10 MHz distribution amplifier -- the ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are wonderful parts, but the large signal frequency response with a 100 ohm load is less than desired for a 10 MHz distribution amplifier. 73 Bill wa4lav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
li...@rtty.us said: You *could* use transformers or filters to transform to higher impedance, but they add phase shift. Phase shift is a problem if it changes (over time, temperature, vibration, phase of the moon...). Change in phase = change in time = signal is degraded. Transformers are handy for providing isolation. How significant are the phase shifts through a transformer relative to other sources of trouble? How much trouble do ground loops cause? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Hi It's always a that depends sort of thing. If you are after total perfection, then indeed any phase shift is suspect. That includes the shift from the delay in the op amp. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Wednesday, February 29, 2012 3:56 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...? li...@rtty.us said: You *could* use transformers or filters to transform to higher impedance, but they add phase shift. Phase shift is a problem if it changes (over time, temperature, vibration, phase of the moon...). Change in phase = change in time = signal is degraded. Transformers are handy for providing isolation. How significant are the phase shifts through a transformer relative to other sources of trouble? How much trouble do ground loops cause? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Hi Very cool. How much power can you run through the device? Put another way, if you drive it with +13 dbm do all the numbers get 5 db better? I doubt very many of us will be worrying about weather it's below -153 at 10 Hz or not… Bob On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote: The attached plot indicates the phase noise performance obtainable with a wideband FET (OPA653) input opamp. With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz at 1kHz offset and around -154dBc/Hz at 10Hz offset. A quieter test source would be useful particularly for offsets below 10Hz. Bruce OPA653PN2.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
The datasheet indicates that an input of +13dBm should be OK albeit with somewhat more 3rd harmonic distortion (~-65dBc) in the output. I'll unearth the prototype single transistor (2N5943) transformer feedback discrete buffer and use it to boost the signal before the splitter. I'll also measure its phase noise, or at least attempt to do so as its likely to be very quiet. The OPA653 was mounted on the TI evaluation board using its internal feedback resistors to set the gain to 2x before the 2x attenuation produced by the source termination and load resistors. The board was powered by a couple of HP E3611A bench supplies. Its likely that the low frequency power supply noise modulation of internal opamp capacitances (and hence the output phase) is greater than that due to opamp noise. Measurements with quieter power supplies may be useful. The OPA653 is a voltage feedback amplifier, a current feedback amp like the AD8007 is likely to have a somewhat higher phase noise floor (+6dB) due to the inverting input noise current (22.5pA/rtHz) flowing in the feedback network resistors (2 x 500 ohm for a gain of 2 ). Bruce Bob Camp wrote: Hi Very cool. How much power can you run through the device? Put another way, if you drive it with +13 dbm do all the numbers get 5 db better? I doubt very many of us will be worrying about weather it's below -153 at 10 Hz or not… Bob On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote: The attached plot indicates the phase noise performance obtainable with a wideband FET (OPA653) input opamp. With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz at 1kHz offset and around -154dBc/Hz at 10Hz offset. A quieter test source would be useful particularly for offsets below 10Hz. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Just a FYI, some op amps have lower distortion in inverting mode than as a follower. This is not intuitively obvious since a follow has maximum feedback, which would imply the best linearity. However the distortion as a follower is due to the common mode rejection of the op amp. That is the inverter has the front end differential pair at a virtual ground while the follower moves the differential pair with the signal. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
A lower limit to the phase noise floor of an opamp can be estimated from its output noise and the output signal level. Half of the output noise power contributes to PM, the other half to AM. At low offsets modulation of internal capacitances by power supply noise and opamp noise modulates the phase shift produced by the opamp. Such modulation occurs even when the amplifier isnt driven into saturation. The same PM mechanisms occur in discrete amplifiers. Keeping the dc gain low is helpful in reducing phase noise. This doesnt mean AC coupling is a useful solution it isnt as a high dc gain from an input base of a BJT to its collector will produce significant modulation of its collector base capacitance and the phase shift of the amplifier. Shunting output load resistors with inductors can be useful in reducing such phase modulation, merely using a capacitor to couple the output to the next stage has no effect on close in phase noise produced by the amplified input noise (or power supply noise - e.g. via a bias divider). Discrete JFETs tend to be somewhat noisier than BJTs for low impedance sources so using a JFET input device isnt usually as effective as using a BJT at least for 50 ohm sources. Bruce Bill Fuqua wrote: Discrete amplifiers are always less noisy than integrated amplifiers. If you want really low noise design a one with JFETs and Bipolar transistors. I am trying to understand the contribution to phase noise by the opamps. Perhaps the threshold is shifting and amplifier is being driven to saturation? I am new to this group but have had lots of RF experience and weak signal detection experience. 73 Bill wa4lav Date: Tue, 28 Feb 2012 07:34:09 -0500 From: Bob Camp li...@rtty.us Hi Very cool. How much power can you run through the device? Put another way, if you drive it with +13 dbm do all the numbers get 5 db better? I doubt very many of us will be worrying about weather it's below -153 at 10 Hz or not? Bob On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote: The attached plot indicates the phase noise performance obtainable with a wideband FET (OPA653) input opamp. With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz at 1kHz offset and around -154dBc/Hz at 10Hz offset. A quieter test source would be useful particularly for offsets below 10Hz. Bruce OPA653PN2.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. William L. Fuqua III P.E. Sr. Electrical Engineer CP 177 Chemistry Physics Building Department of Physics and Astronomy University of Kentucky Lexington,KY 40506-0055 Phone: 1-859-257-4155 e-mail: wlfuq...@uky.edu ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
You need to look at the driving impedance before you declare one technology quieter than another. That is, you have voltage noise and current noise. For low driving impedance, bipolar will be quieter since current noise will not be significant, plus a bipolar will have lower thermal noise. For high impedance, JFET may be a better solution. Opamps are around 1nv/rootHz these days. That isn't all that easy to achieve discretely. Noise is proportional to the square root of the bandwidth, so less is more. But that is broadband noise. I'm not sure about phase noise. On 2/28/2012 10:41 AM, Bill Fuqua wrote: Discrete amplifiers are always less noisy than integrated amplifiers. If you want really low noise design a one with JFETs and Bipolar transistors. I am trying to understand the contribution to phase noise by the opamps. Perhaps the threshold is shifting and amplifier is being driven to saturation? I am new to this group but have had lots of RF experience and weak signal detection experience. 73 Bill wa4lav Date: Tue, 28 Feb 2012 07:34:09 -0500 From: Bob Camp li...@rtty.us Hi Very cool. How much power can you run through the device? Put another way, if you drive it with +13 dbm do all the numbers get 5 db better? I doubt very many of us will be worrying about weather it's below -153 at 10 Hz or not? Bob On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote: The attached plot indicates the phase noise performance obtainable with a wideband FET (OPA653) input opamp. With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz at 1kHz offset and around -154dBc/Hz at 10Hz offset. A quieter test source would be useful particularly for offsets below 10Hz. Bruce OPA653PN2.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. William L. Fuqua III P.E. Sr. Electrical Engineer CP 177 Chemistry Physics Building Department of Physics and Astronomy University of Kentucky Lexington,KY 40506-0055 Phone: 1-859-257-4155 e-mail: wlfuq...@uky.edu ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Hi I think the tradeoff of harmonics still better than -60dbc is fine if the floor does indeed drop a few more db. For time nut applications, it's going to be the phase noise close to carrier that matters. Harmonics with reasonable terminations would not be the big issue. It will be interesting to see if the supplies really do contribute to the close in noise in this case. If so, there are a lot of ways to take care of that. My guess is that a couple simple linear regulators will take care of it if there's an issue there. If you have a setup to do so, take a look at the output return loss next time it's up and running. One thing this approach *should* do is to give you very good return loss. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Tuesday, February 28, 2012 1:21 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...? The datasheet indicates that an input of +13dBm should be OK albeit with somewhat more 3rd harmonic distortion (~-65dBc) in the output. I'll unearth the prototype single transistor (2N5943) transformer feedback discrete buffer and use it to boost the signal before the splitter. I'll also measure its phase noise, or at least attempt to do so as its likely to be very quiet. The OPA653 was mounted on the TI evaluation board using its internal feedback resistors to set the gain to 2x before the 2x attenuation produced by the source termination and load resistors. The board was powered by a couple of HP E3611A bench supplies. Its likely that the low frequency power supply noise modulation of internal opamp capacitances (and hence the output phase) is greater than that due to opamp noise. Measurements with quieter power supplies may be useful. The OPA653 is a voltage feedback amplifier, a current feedback amp like the AD8007 is likely to have a somewhat higher phase noise floor (+6dB) due to the inverting input noise current (22.5pA/rtHz) flowing in the feedback network resistors (2 x 500 ohm for a gain of 2 ). Bruce Bob Camp wrote: Hi Very cool. How much power can you run through the device? Put another way, if you drive it with +13 dbm do all the numbers get 5 db better? I doubt very many of us will be worrying about weather it's below -153 at 10 Hz or not. Bob On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote: The attached plot indicates the phase noise performance obtainable with a wideband FET (OPA653) input opamp. With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz at 1kHz offset and around -154dBc/Hz at 10Hz offset. A quieter test source would be useful particularly for offsets below 10Hz. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Bill wrote: At what frequency do you have 1 nv per square root Hz with opamp and what opamp ? With most op-amps suitable for a 10 MHz distribution amp, the input voltage noise is specified at 100 kHz or greater. For example, the OPA653 that Bruce tested is specified for 6.1 nV/rtHz (typical) at 100kHz and the graph shows that it has a 1/f noise corner in that vicinity, with a noise density greater than 100 nV/rtHz at 10 Hz. There are op-amps that are likely suitable for 10 MHz distribution that have lower input voltage noise than the OPA653 (again, generally specified at 100 kHz or 1 MHz): AD811 (1.9); AD8007 (2.7); AD8010 (2); ADA4899 (1); EL5166 (1.7); EL5236/7 (1.5); OPA695 (1.8); THS3001 (1.6); and THS3112 (2.2). Many of these are current-feedback amps, but if you keep the resistance at the inverting input low (200 to 75 ohms, depending on the particular amp) the inverting input current noise will be lower than the noninverting input voltage noise. If the amp has sufficient output current to drive a back-terminated 50 ohm load with authority (the OPA653 is a bit marginal in this respect, IMO), there should be no problem driving such a feedback network plus the load. I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being capable of useful operation as a 10 MHz distribution amplifier -- the ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are wonderful parts, but the large signal frequency response with a 100 ohm load is less than desired for a 10 MHz distribution amplifier. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Yes, there will be no set rule. You would need to try both inverting and not inverting for each op amp. On 2/28/2012 10:22 PM, Bruce Griffiths wrote: For the OPA653 the noninverting configuration has lower distortion at least for 2V pp outputs. Bruce gary wrote: Just a FYI, some op amps have lower distortion in inverting mode than as a follower. This is not intuitively obvious since a follow has maximum feedback, which would imply the best linearity. However the distortion as a follower is due to the common mode rejection of the op amp. That is the inverter has the front end differential pair at a virtual ground while the follower moves the differential pair with the signal. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Op amps have been used for quite a while. I have used buffer amps called lh003s preceded by a opamp (that I do not recal)to create a 2 X gain. They were power hungry. It looks like these have very wide bandwidth. You really do not need that wide of a bandwidth. Maybe 20 Mhz for a 10 Mhz ref. Good article. Regards Paul WB8TSL On Mon, Feb 20, 2012 at 11:28 AM, Michael Baker mp...@clanbaker.org wrote: Hello, Time-Nutters-- Here is a link to a TI app note on using op-amps for RF. It occurred to me that this might work OK for distribution of the ref freq from a GPSDO... http://www.ti.com/lit/an/**slyt102/slyt102.pdfhttp://www.ti.com/lit/an/slyt102/slyt102.pdf Mike Baker --- __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
On Mon, 20 Feb 2012 11:28:01 -0500 Michael Baker mp...@clanbaker.org wrote: Here is a link to a TI app note on using op-amps for RF. It occurred to me that this might work OK for distribution of the ref freq from a GPSDO... http://www.ti.com/lit/an/slyt102/slyt102.pdf Depends on what you want to do and what your specs are. If you just need a 10MHz signal that looks ok, then an Opamp is an obvious choice. It is by far simpler to design than a discrete solution (especially today, when nobody knows how a transistor works). Just plug it in, a few resistors around it and you're done. But there are two things that the article does not tell you: Noise and power. Opamps (used as amplifiers) generally have a higher noise than equivalent discrete transistor circuits and use more power. So if you care about jitter, noise and want to be in the nutty of the time-nutty region, then there is no way around designing your own distribution amplifier using discrete components. And just for reference: There are already Opamps around with a gain bandwidth product of 1GHz. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
On Mon, Feb 20, 2012 at 7:32 PM, Steve iteratio...@gmail.com wrote: Decent frame? Plenty of internal room for tweaking? What make and model? You've got me interested! You have to keep watching, every day or two. thinks like this come up. Craigs list also it you live in a place with lots of video production Look up eBay item 250977591548. The description is still on the seller's page. I figured it was worth the cost to ship even if All I got as the metal case. The case cleaned up ok. the stickers and velcro came off. It is powered by a pair of LM7805 and LM7905. I can double the voltage with minor hardware hacking. parts are rated for more than triple voltage but that requires major hardware hacking. Steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OP-Amps for 10MHz distribution...?
Mike, op amps for that purpose should be available from a lot of companies. They are not created all equal. My latest own design of a distribution amp involves one AD8007 input stage with variable gain and 8 AD8007 output stages. This design is good for a channel to channel isolation of 90 dB and an output to input isolation of 113 dB. The AD8007 has VERY small distortion and I needed to build a lowpass/bandpass filter to measure it because NONE of my sources (HP3325/HP8660) was clean enough that it could match the AD8007. The -125 dBm noise floor of my sprectrum analyser were just enough to see any amplifier produced noise. The power supply design may be as important as the choice of amplifier. Best regards Ulrich Banget -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Michael Baker Gesendet: Montag, 20. Februar 2012 17:28 An: time-nuts@febo.com Betreff: [time-nuts] OP-Amps for 10MHz distribution...? Hello, Time-Nutters-- Here is a link to a TI app note on using op-amps for RF. It occurred to me that this might work OK for distribution of the ref freq from a GPSDO... http://www.ti.com/lit/an/slyt102/slyt102.pdf Mike Baker --- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
