[SOLVED] Differential Amplifier simulation using Synopsys Hspice

[ehsanaiman]

Hello,
I want to ask some questions on this differential amplifier circuit that I referred in article "Design of CMOS Two-stage Operational Amplifier for ECG Monitoring System Using 90nm Technology by Moulahcene F Bouguechal N Benacer I Hanfoug S".



1. Can somebody explain to me about current mirror operation in simpler words?
2. If I want to build and simulate the schematic, do I need to add dc current source Iref in my schematic?

Im using Hspice with 90nm technology. Thank you.

 

[erikl]

View attachment 141437
1. Can somebody explain to me about current mirror operation in simpler words?

The current mirror M8 -> M5 regenerates (or multiplies) Id(M5) = Id(M8) • (W/L(M5)) / (W/L(M8)) , similar for the mirror M8 -> M7
Id(M8) = Iref

2. If I want to build and simulate the schematic, do I need to add dc current source Iref in my schematic?

Yes, sure. Use the idc current source.

 

[ehsanaiman]

Thank you for answering my questions, but I didnt get same gain as the circuit in article, although I have designed circuit according to all W/L ratio and capacitance. What is probably the cause of different gain obtained from same circuit with same design?

 

[erikl]

What is probably the cause of different gain obtained from same circuit with same design?

Same process? If not, this will be the reason. If so, probably different simulation models.

 

[ehsanaiman]

It is possible if using different software; Cadence Virtuoso and Synopsys HSpice giving different simulation results even the same process technology?

 

[erikl]

It is possible if using different software; Cadence Virtuoso and Synopsys HSpice giving different simulation results even the same process technology?

Yes, as I stated above: probably different simulation models.

Different design systems might not use the same simulator (Cadence Virtuoso: mainly Spectre ; Synopsys: HSpice), very probably they will use different transistor models.

You could try, find & check/compare them.

 

[ehsanaiman]

Alright sir, thank you for your fine explanations. Those will help me in designing new amplifier based on current circuit.