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Where To Find This Example

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Design Notes

CMOS OpAmp project

This project shows a CMOS Operational Amplifier designed with AWR Generic Silicon Process Design Kit. This OpAmp has cascoded first stage to get higher gain without having to add another common-source stage. The first stage is followed by level shifter and output stage. OpAmp also has a simple bias circuit located in the left part of the schematic.

This project also shows the measurement setups to simulate basic OpAmp characteristics; transfer function (Bode plot), CMMR, PSRR, DC function and pulse response.


This project is divided into multiple schematics. Each schematic represents as test bench to measure different OpAmp characteristic. The name of the schematic tells what OpAmp characteristic it is used to simulate. All the measurements are done with HSpice DC, AC and transient solvers.

Open the schematics and corresponding graph to see the simulation setups and curves. See the correspondence below:

"AC test" -> "Bode Plot"

"CMRR test" -> "CMRR"

"PSRR test" -> "PSRR"

"DC test" -> "DC transfer"

"Transient test1" -> "UnityGain Pulse Response"

"Transient test2" -> "Pulse Response"

"Inet current density" test bench is used to annotate current density of each Inet to layout. To see the current densities in the layout open the schematic "Inet current density" and choose View > New Layout View.

The enabled measurements use APLAC simulators. If your license includes HSPICE, then enable all equations in Output Equations, and enable all measurements in all graphs, and simulate to see HSPICE simulation results. Due to the simplicity of the circuit, transient simulation tolerances may need to be tightened for a more precise match between the two simulators in the "UnityGain Pulse Response" graph (e.g. select Options > Default Circuit Options...; click HSPICE Sim tab > Show Secondary button, and set TRTOL=6; click APLAC Sim tab > Show Secondary button, and set Truncation Error Mode to Charge).

To see more advanced OpAmp project with simulations over PVT open the example project "OpAmpNPN". You can also find more information about Inet current annotations from example project "Current_Density_Annotation".

Schematic - OP_amp

Schematic - AC_test

Schematic Layout - OP_amp

Graph - Bode Plot

Graph - UnityGain Pulse Response

Graph - Pulse Response