Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Alex is having email trouble so I'll post on his behalf. He adds this useful resource to the discussion: > http://audioworkshop.org/downloads/AMPLIFIERS_OSCILLATION_BJT_CIRCUITS.pdf > > 73 > KJ6UHN Alex ___ time-nuts mailing list --

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

The transition frequency of a transistor is more of a ballpark figure of merit than a device specific constant, as it is also a function of how the device is biased. Since most amplifiers and oscillators need power gain to operate, current gain is usually needed (though you could use voltage gain

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Sat, 02 Jul 2016 14:09:44 -0500 David wrote: > If you can find it, "Preventing Emitter-follower Oscillation" by > Michael Chessman and Nathan Sokal has an analysis of negative > resistance oscillation in transistors and why adding dampening to one > lead is often

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Sat, 2 Jul 2016 19:00:24 +0200, you wrote: >On Fri, 1 Jul 2016 12:28:44 -0400 >Bob Camp wrote: > >> Real cascode circuits can be built with RF transistors. They also can be >> simulated. >> Simulating them with the “standard” models is a PIA. The issue is that the >>

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

I vaguely remember seeing designs where a through hole transistor like a 2N5179 had a ferrite bead slipped over the base to keep it stable. Although this works, it degrades the performance of the transistor. I prefer to put a resistor in series with the collector instead of the base. Since the

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Hi Yes, you can also look at it as “damping” or" de-Q-ing”. You trade off a bit of isolation for stability. Put another way, the resistor will take the isolation of the stage down a bit. Another practical point on the stage - you want the base bypass as close to the end of that resistor as

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Fri, 1 Jul 2016 12:28:44 -0400 Bob Camp wrote: > Real cascode circuits can be built with RF transistors. They also can be > simulated. > Simulating them with the “standard” models is a PIA. The issue is that the > inductance > of the package is not de-embedded from the test

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Fri, 1 Jul 2016 15:45:36 -0400 Scott Stobbe wrote: > If you need higher output resistance you will have to move to a FET based > approach. If you need less than 1 pF of output capacitance you will need a > better transistor and care in how you physically construct

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Hi Works for both. Bob > On Jul 1, 2016, at 2:54 PM, Hal Murray wrote: > > > kb...@n1k.org said: >> There is also the somewhat non-intuitive need to stick a low value resistor >> in the base. Done properly, they are very reproducible and reasonably >> insensitive to

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

There are a plethora of ways to build up a current source. The nice thing about spice is you can start with a generalized model to see which way you need to go. For a bipolar current source (sampling current at the emitter) you are going to achieve a maximum output resistance of beta*ro with an

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

kb...@n1k.org said: > There is also the somewhat non-intuitive need to stick a low value resistor > in the base. Done properly, they are very reproducible and reasonably > insensitive to load. Is that required for real circuits or just for the simulations? -- These are my opinions. I hate

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Hi > On Jul 1, 2016, at 7:56 AM, Attila Kinali wrote: > > Moin, > > Thanks everyone for the answers! > > On Mon, 20 Jun 2016 01:45:24 -0400 > Charles Steinmetz wrote: > >> The transation frequency of the current source transistor is part of the >>

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Moin, Thanks everyone for the answers! On Mon, 20 Jun 2016 01:45:24 -0400 Charles Steinmetz wrote: > The transation frequency of the current source transistor is part of the > cause, but the primary cause is generally the capacitance of the CS > output node to ground.

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Attila wrote: Having put the circuit through Spice, I see that the current through the tail fluctates violently during the time when the current switches from one transistor of the pair to the other. The reason for this seems to be that the f_t of the current source transistor is too low to

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

National's discrete products databook includes rough descriptions of the various processes, die shots showing geometry, and lists which transistors are fabricated on which process. On Sun, 19 Jun 2016 22:25:28 +, you wrote: >Once upon a time I came across a document from National

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On Sunday, June 19, 2016 07:23:09 PM Attila Kinali wrote: > Good evening, > > I have recently been looking into BJT's and their switching properties. > Because a time-to-amplitude converter does similar things as I would like > to, I have been looking in what people do with those. First thing

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

>Why do people use general purpose transistors in these places, even >though RF transistors definitly improve switching behaviour? Commercial designs do use RF transistors but only old ones are documented. The Tektronix 7A11 uses 2 GHz PNPs and 1 GHz NPNs but its design is unusual since it can

[time-nuts] Switching transistors, current sources, nonidealties and noise

Once upon a time I came across a document from National Semiconductor that talked about their transistor product line. At the time they made less than 100 different transistor dies... but sold them under 10,000+ different part numbers.Some were just packaging variations. Maybe some

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

On 6/19/16 10:23 AM, Attila Kinali wrote: Good evening, I have recently been looking into BJT's and their switching properties. Because a time-to-amplitude converter does similar things as I would like to, I have been looking in what people do with those. First thing that strikes me as kind of

Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

Hi Leakage Bob > On Jun 19, 2016, at 1:23 PM, Attila Kinali wrote: > > Good evening, > > I have recently been looking into BJT's and their switching properties. > Because a time-to-amplitude converter does similar things as I would like to, > I have been looking in what

[time-nuts] Switching transistors, current sources, nonidealties and noise

Good evening, I have recently been looking into BJT's and their switching properties. Because a time-to-amplitude converter does similar things as I would like to, I have been looking in what people do with those. First thing that strikes me as kind of odd is that almost all designs I have seen