One thing to be wary of, especially with 74AC running at full voltage,
is that if you analog-bias an input midway, the internal supply current
can go up. If the AC coupled input drive signal is big enough, then the
input will spend little time near the middle threshold, so it's OK. If
the
Hi
If you want to get the 74AC74 (or better the 74LVC74) running it’s best:
1) Power it off of 5.50V
2) Transform the drive signal so that it presents 5.5 to 5.8V p-p to the
gate input.
3) Bias the AC signal so that it swings from about 0 to 5.5V
Bob
> On Jul 19, 2020, at 8:18 AM, Magnus
Hi Rick,
On 2020-07-19 04:30, Richard (Rick) Karlquist wrote:
>
> Yes, the simple pair of resistors doesn't work well on TTL.
> That was probably done by a production engineer, who was
> working above his pay grade. We can't all be Len Cutler.
Sounds very reasonable. It's a crude hack and works
On 7/18/2020 6:25 PM, Magnus Danielson wrote:
Hi,
A similar approach is used in the 10811 replacement oscillator setup for
the 5065, where a 7474 is used to divide 10 MHz to 5 MHz. Signal
conditioning consists of a DC-blocking cap and a pair of resistors to
bias the mid-point. The produced
Hi,
A similar approach is used in the 10811 replacement oscillator setup for
the 5065, where a 7474 is used to divide 10 MHz to 5 MHz. Signal
conditioning consists of a DC-blocking cap and a pair of resistors to
bias the mid-point. The produced noise is at least 10 dB worse than you
would expect.
Hi
One very simple “fix” for the low voltage sine wave:
Put in an L network and transform the load output to a higher
impedance. Voltage goes up as square root of impedance change.
For modest (2X ~ 4X) voltage changes, the lowpass L network still
has modest Q and low component sensitivities.
A long time ago I used a 74AC74 to prescale a 100MHz VCO down to 25, the
74AC74 was AC coupled to the VCO and the signal was a fraction of a volt.
Worked quite well.
Probably not time-nuts quality but in a pinch it did the job at the time.
Didier
On Sat, Jul 11, 2020 at 9:37 PM Alex Pummer
Hi Perrier
https://www.y-ic.es/datasheet/3b/74F569SC.pdf will work
73
KJ6UHN
Alex
On 7/11/2020 3:00 PM, Perry Sandeen via time-nuts wrote:
Learned List,
On previous posts I was looking for a PDIP package 100 MHz decade divider.
Reading just the front of the data sheet I thought that the
Hi
HC is the *slower* version of AC. If it makes it to 50 MHz, you are doing well
…..
Bob
> On Jul 11, 2020, at 6:00 PM, Perry Sandeen via time-nuts
> wrote:
>
> Learned List,
> On previous posts I was looking for a PDIP package 100 MHz decade divider.
> Reading just the front of the data
The 74XX160/74XX162 is the decade divider that runs at maximum
clock rate for the chip. Meaning no external feedback is
necessary to make it work at divide by 5/10.
The 74XX161/74XX163 can only divide by powers of 2 at maximum
clock rate. You have to add feedback to divide by 5 and THAT
is
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