Understand a PSK circuit

Thread Starter

tsunakata

Joined Nov 21, 2019
1
I'm new in telecommunications and I want to understand how this Phase Shift Keying circuit work, I don't have a clear idea of how the opamp is helping to get the phase shift keying. for your info the first signal generator is giving a sine signal (5kHz/5V) and the second a square signal (1kHz/5V). I done this circuit and knew it works, but I want to know how and why, thanks.sketch-1574371389380.png
 

crutschow

Joined Mar 14, 2008
23,487
I done this circuit and knew it works, but I want to know how and why, thanks.
When the transistor is off, the opamp has the same signal applied to both inputs, thus it operates as a gain-of-one follower.
When the transistor is on, shorting the plus input to ground, the opamp acts as an inverter with a gain of -1, thus changing the phase by 180 degrees.
 
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