OPA189: May OPA189 suit use in single-end to differential output application?

Bogey,

You have specified a supply of +/-15 V and a differential output of 0 to -30 V. There are two issues with this; the output swing is being specified with a low end limit of -30 V with a -15 V rail, and as in the previous e2e discussions no op amp can swing to the supply rail. Also, the OPA189/OPA2189 is likely to be unstable driving 5 to 10 nF. The datasheet Figure 26, Small-Signal Overshoot vs Capacitive Load, shows that with a 1 nF load the overshoot percentage is in the 40 to 45 % range indicating that the phase margin is only about 30 to 35 degrees. If the capacitive load is further increased to 5 or 10 nF the phase margin will not be sufficient to maintain stability. Therefore, if the OPA189 can drive capacitive load circuit compensation will be required.

I show below a basic OPA2189 amplifier circuit that provides a differential output. I like to use two inverting stages so that the noise gain of each stage is the same resulting in like bandwidths. A 100 Ohm Riso is added in series with the 10 nF load to stabilize the op amps. You can see the TINA Spice simulation results here:

You can see from this result that a 60 Vpp output is achieved with 30 Vpp input.

Regards, Thomas

Precision Amplifiers Applications Engineering

Hello Bogey,

Please see that attached TINA simulation file for the OPA2189 differential output amplifier circuit.

Regards, Thomas

Precision Amplifiers Applications Engineering

OPA2189_DiffOut_01.TSC