Hello all,
I'm building a lock-in amplifier circuit based on the AD630 chip for an optical measurement system (circuit is similiar to this one: http://blockyourid.com/~gbpprorg/mil/cavity/lock/SimpleLockInAmplifier.pdf)
Anyways, I've noticed that the output is negative, so I need to modify the phase of the reference signal. I've found a simple phase shifter circuit (attached), but I can't find a lot of info on the circuit itself. After building it (with R = 10k and C = 23nF) I get a 90degree phase change of a square wave input at each extreme of the potentiometer (100k pot), but in between these two extremes the waveform changes significantly from a square wave profile. I believe the choice of components are designed for a 5kHz, can anyone suggest suitable values for a 1kHz wave (I'm assuming that that is the reason the output isn't square-wave like.
Also, do I need to use an op-amp with both negative and postive supply rails? (I'm just using a single supply op-amp (TLC271)).
Any info (links or otherwise) would be much appreciated.
Thanks!
I'm building a lock-in amplifier circuit based on the AD630 chip for an optical measurement system (circuit is similiar to this one: http://blockyourid.com/~gbpprorg/mil/cavity/lock/SimpleLockInAmplifier.pdf)
Anyways, I've noticed that the output is negative, so I need to modify the phase of the reference signal. I've found a simple phase shifter circuit (attached), but I can't find a lot of info on the circuit itself. After building it (with R = 10k and C = 23nF) I get a 90degree phase change of a square wave input at each extreme of the potentiometer (100k pot), but in between these two extremes the waveform changes significantly from a square wave profile. I believe the choice of components are designed for a 5kHz, can anyone suggest suitable values for a 1kHz wave (I'm assuming that that is the reason the output isn't square-wave like.
Also, do I need to use an op-amp with both negative and postive supply rails? (I'm just using a single supply op-amp (TLC271)).
Any info (links or otherwise) would be much appreciated.
Thanks!
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