spectrum
Member
hello all,
hope i'm not annoying you with these stupid circuit tests, i studied electronic at school, but i have never developed a circuit with op amps and impedance problems, so i am looking for some help and clarifications.
My problem is: i have a sinusoidal wave 200Vpp signal that is applied as a carrier to an antenna.
In particular circumstances this carrier signal sometime can have 210Vpp and some others 200Vpp. I need to reduce this voltage and have as output in some way a dc level <5V, or a 1/0 logic state to give it as input to a microcontroller.
But i'm not looking for the best ready solution, i want try to do a circuit by myself, understanding things step by step.
I was trying dividing and rectifiying directly with a schottky, without success, so attached there is a diagram with my new approach.
So i've tought to reduce the voltage with some MOhms resistors, to avoid to create problem to antenna transmission. So, antenna still works fine. Then, i've tought to give the signal to an op.amp, to have low impedance and more current available as output. Then to rectify and have a DC level between 0 and 5V.
So i have some questions:
1) in the point "A" i was expecting a 20Vpp sinusoidal wave, but with x10 oscilloscope probe i see a 2Vpp signal.
2) in the point "B" i was expecting a non-inverted signal with same as the signal in "A". I see a 5 Vpp only positive signal, with negative part cutted and a little cutted at 5V. I think that is becouse i used an only positive power for the op-amp, but i don't understand the amplification effect, idoes it should have gain 1 in this config ?
3) in point C is finally see a wave like in B, with a more clean cut near 0,2V.
In particular, i can't understand why i have so different voltage in "A" from what i was expecting.
Thanks, angelo
hope i'm not annoying you with these stupid circuit tests, i studied electronic at school, but i have never developed a circuit with op amps and impedance problems, so i am looking for some help and clarifications.
My problem is: i have a sinusoidal wave 200Vpp signal that is applied as a carrier to an antenna.
In particular circumstances this carrier signal sometime can have 210Vpp and some others 200Vpp. I need to reduce this voltage and have as output in some way a dc level <5V, or a 1/0 logic state to give it as input to a microcontroller.
But i'm not looking for the best ready solution, i want try to do a circuit by myself, understanding things step by step.
I was trying dividing and rectifiying directly with a schottky, without success, so attached there is a diagram with my new approach.
So i've tought to reduce the voltage with some MOhms resistors, to avoid to create problem to antenna transmission. So, antenna still works fine. Then, i've tought to give the signal to an op.amp, to have low impedance and more current available as output. Then to rectify and have a DC level between 0 and 5V.
So i have some questions:
1) in the point "A" i was expecting a 20Vpp sinusoidal wave, but with x10 oscilloscope probe i see a 2Vpp signal.
2) in the point "B" i was expecting a non-inverted signal with same as the signal in "A". I see a 5 Vpp only positive signal, with negative part cutted and a little cutted at 5V. I think that is becouse i used an only positive power for the op-amp, but i don't understand the amplification effect, idoes it should have gain 1 in this config ?
3) in point C is finally see a wave like in B, with a more clean cut near 0,2V.
In particular, i can't understand why i have so different voltage in "A" from what i was expecting.
Thanks, angelo