I have the following request:
I want to stop a common integrator (which should generate a defined slew rate for a square wave signal) exactly at zero (0 Volt) due to the return-to-zero coding of the interface.
In reality, the integrator will be supplied with a push-pull stage (+/- 5V), a third transistor would be switched against GND.
I have tried two comparators (LM393), whose output signal would be detected by a digital logic and the logic would then switch the push-pull stage to idle:
The problem: As you can already see in the simulation, there is a bigger phase offset (this is only the result of one comparator covering the positive threshold).
Can anyone think of a simple and fast solution? Maybe just one transistor?
Best Answer
This is a little crude, but I think it does what you are asking (sorry for the screen grab but links from the schematic editor are not working for me right now)
R2 and R3 bias Q1 so it turns on when the emitter is near 0V. They're not optimized and the turn-on will vary with temperature.
If you want something much more precise, consider a comparator driving an analog switch across C1.