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2022-08-16, 14:45:45
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Author Topic: Need amplifier circuit for SN54AHC174 hex D-FF Output and faster rise time  (Read 478 times)

Group: Tinkerer
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As the title states:

I have a slow output from a SN54AHC174 hex d-type Flip-flop and need to amplify the output to +30v with a rise time of 10ns or less.

I just need enough current to run it.

All help and advice is appreciated.
   

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Enjoy your trek through life but leave no tracks
Grum hi, what is it your after ? I have some of that series of devices they went all that fast compared to 74hc type that i tried
are we talking about rise time, propagation delay or fall time or the fastest narrowest spike you can generate ?
if that’s the case logic is far too slow at light spread approach  8)

If you go back to the old dally thread some of the old Emjoykin2 posts are what you need to go through.

Any way back-in the old days fast scopes used a tunnel diode to sync the time base, they were fast down to 1  or 2 Nano secs you can find data for them on Youtube.

Sil
   

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I want to use the output of the SN54AHC174 to trigger a 2N5551 transistor in avalanche mode, which requires a pulse of at least 10v with less than 10ns rise.
   

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As the title states:

I have a slow output from a SN54AHC174 hex d-type Flip-flop and need to amplify the output to +30v with a rise time of 10ns or less.

I just need enough current to run it.

All help and advice is appreciated.

It depends on the current you want. If the need is limited to about 1W, a classical bipolar transistor like the 2N3866 is perfect. It is driven by its base with a 100 to 470 ohm resistor, and the collector is connected to the 30v power supply by a resistor. Output on the collector. Be careful, the signal will be inverted.
For more power (2,5 W) but a slower switching which should still be around 10ns, there is the 2N3553.
Beyond that, you should not look for switching transistors, but HF power transistors for V/UHF amplifiers.



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It depends on the current you want. If the need is limited to about 1W, a classical bipolar transistor like the 2N3866 is perfect. It is driven by its base with a 100 to 470 ohm resistor, and the collector is connected to the 30v power supply by a resistor. Output on the collector. Be careful, the signal will be inverted.
For more power (2,5 W) but a slower switching which should still be around 10ns, there is the 2N3553.
Beyond that, you should not look for switching transistors, but HF power transistors for V/UHF amplifiers.

1W is sufficient.
Will the signal at the base affect the rise time of the 2N3866?

   
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1W is sufficient.
Will the signal at the base affect the rise time of the 2N3866?

It's hard to say. The switching by the transistor may be faster than the signal that controls it, because there is a threshold effect around the diode bend that constitutes the base/emitter junction.
If the base drive signal is of sufficient amplitude and not too slow, say a few tens ns, then with a 2N3866, a switching of less than 10 ns should be achieved without problem. The best would be to add a small capacitor in parallel on the resistor driving the base (for example 220 pF), in order to favor the di/dt.


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Both 2N553 and 2N3866 appear to be obsolete and no longer manufactured.

   
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