ultrasoundguy2
Bioengineer
- Jul 1, 2014
- 28
hi all.
really struggling with an issue Im having with a power op amp.
We are getting a distortion in the output waveform, a copy of it is below
we are driving a capacitive load and thus, have impedance matched the output of the power op amp (PA119) to the transducer.
The series R and transformer correct the real while the inductor checks the reactive.
Impedance matching is not the issue.
A copy of the circuit is below
We get this distortion whether the transformer 2ndary is connected to anything or not.
We get distortion regardless of the CC value (capacitor type, variable capacitors, etc).
We get the issue on two entirely prototype systems with independent equipment on each.
We do not get the issue if we drive a completely resistive but equivalent load (15ohms)
We are even using low inductance power resistors (for 10ohm) which keep the reactive load low.
You guys must have experience with this?
I mean is just a low inductance load?
Ive contacted the people that make the chip and they didn't have anything to help.
the only way I was able to correct this alittle was by shunting the output with an somewhat opposite reactive load (The R37)
It pretty much clears up any distortion..
with that said, we burn 3/4 of the power going through these two resistors.
A way to stabilize it without this resistor would be desirable
Any if anyone is really good out there, a way to go from a 1.5ohm source impedance to 35ohm while limited to 3 amps without using resistor would be great too..
really struggling with an issue Im having with a power op amp.
We are getting a distortion in the output waveform, a copy of it is below
we are driving a capacitive load and thus, have impedance matched the output of the power op amp (PA119) to the transducer.
The series R and transformer correct the real while the inductor checks the reactive.
Impedance matching is not the issue.
A copy of the circuit is below
We get this distortion whether the transformer 2ndary is connected to anything or not.
We get distortion regardless of the CC value (capacitor type, variable capacitors, etc).
We get the issue on two entirely prototype systems with independent equipment on each.
We do not get the issue if we drive a completely resistive but equivalent load (15ohms)
We are even using low inductance power resistors (for 10ohm) which keep the reactive load low.
You guys must have experience with this?
I mean is just a low inductance load?
Ive contacted the people that make the chip and they didn't have anything to help.
the only way I was able to correct this alittle was by shunting the output with an somewhat opposite reactive load (The R37)
It pretty much clears up any distortion..
with that said, we burn 3/4 of the power going through these two resistors.
A way to stabilize it without this resistor would be desirable
Any if anyone is really good out there, a way to go from a 1.5ohm source impedance to 35ohm while limited to 3 amps without using resistor would be great too..