How to Create a True Differential Front-End in PSPICE

John La Grou

Other Parts Discussed in Thread: OPA1637

I want to run a true differential circuit (e.g., using OPA1637 diff amp), with a differential input and differential output. I want to measure with diff output parameters using PSPICE.

What's the correct way to configure true differential AC Source waveform? Do I use TWO independent Sources with some kind of polarity flip on one of the Sources? Do I use a single source driving from both ends? Do I use the OPA1637 reference design (see attached) which uses functional blocks that I'm not familiar with? The OPA1637 reference design seems to be driven from identical polarities (not 180/180 differential). And while we're here, what's the correct way to measure a true differential output?

10 months ago

0 Luis Chioye 10 months ago

TI__Mastermind 49375 points

Hi John,

There may be different ways to accomplish this, but one way that has work for me is using the voltage controlled sources arranged as shown below.

The first pair of voltage controlled sources are set on gain of 0.5V/V, and are controlled by the Vdiff source, they set the input signal differential voltage.

The second pair of voltage controlled sources are set on gain of 1V/V, and shift the input differential signal to the desired common-mode voltage, controlled by the DC VICM source.

Thank you and Regards,

Luis

0 John La Grou 10 months ago in reply to Luis Chioye

Intellectual 320 points

Thanks. What is E9-E12, and where do I find these blocks in PSPICE? Looks like some kind of Dependent Source, but I can't find it in the User Guide.

0 Luis Chioye 10 months ago in reply to John La Grou

TI__Mastermind 49375 points

HI John,

This is a Voltage Controlled Voltage Source available in SPICE simulators.

To place a VCVS on your PSPICE for TI schematic, navigate to "Place" on the top menu, -> "PSpice Component"->"Source"->"Controlled Sources"->"VCVS". See image below.

For detailed instructions/PSpice documentation, navigate to top menu, "Help" -> "PSpice for TI Help" and search for "voltage controlled voltage source".