How to simulate 741 CMRR and PSRR ?

[duron999]

how to simulate psrr

I'm doing a layout of 741 op-amp,
however, what configuration can i test the CMRR and PSRR ?
thanks !

 

[Mline7]

how to simulate cmrr

* Differential Mode Gain:
- The AOP is connected in Open Loop with a Low Frequency RC Filter placed between Vout and V- to correctly bias the AOP.
- Also put a Vdm AC input source in series with the RC filter at the V- input to provide the AC differential signal.
- Dot not forget to bias the V+ input with a Vbias source.
- This scheme will provide you with the OpenLoop Gain ADM=Vout/Vdm.

* CMRR:
- Once again use an RC Filter between Vout and V- to correctly bias the AOP in DC.
- Place a capacitor between V+ and V-, it will short V+ to V- in AC, thus connect them in AC for common mode signaling.
- Bias the V+ input with a Vbias voltage source, and a Vcm AC source signal.
- This scheme will provide you with the common-mode gain ACM=Vout/Vcm.
- The CMRR is then simply ADM/ACM


* PSRR:
- Once again use an RC Filter between Vout and V- to correctly bias the AOP in DC.
- Place an VDD (resp. VSS) AC source in series with the positive supply (respectively negative).
- The positive (resp. negative) rejection is PSR+=Vout/VDD (=Vout/VSS)
- The rejection ratio is: PSRR+=VDM/PSR+ (resp. VDM/PSR-)

 

[xwcwc1234]

cmrr 741

I think you can refer to P.E.Allen's analog design book for graphical and spice run reference.

 

[moda]

cmrr lm741

Get more info at that pdf.


**broken link removed**

 

[duron999]

cmrr in op amp 741

Thank all information !!!
Let me try it, thanks !!!

 

[duron999]

positive power supply rejection ratio

If i use cadence for simulation,
can anyone show me the testing circuit schematic ???
I try many time, but it can't work.... thanks !

 

[srivatsan]

how to simulate psrr

Please Post the circuit. That may help.

- vats.

 

[duron999]

how to simulate common mode rejection ratio

Please Post the circuit. That may help.

- vats.

The circuit only contain one LM741, thanks !

 

[jiangwp]

common mode rejection ratio of a 741 ic

For the PSRR

The LM741 positive input port connects the (Vdd/2);
The LM741 negative input port connects the output;
The LM741 output port connects a 1Meg resistor and a 2p capacitor;
The LM741 negative power port connects the negative dc power ;
The LM741 positive power port connects the positive dc power and a ac power supply which amplitude is 1.

 

[duron999]

simulate psrr

For the PSRR

The LM741 positive input port connects the (Vdd/2);
The LM741 negative input port connects the output;
The LM741 output port connects a 1Meg resistor and a 2p capacitor;
The LM741 negative power port connects the negative dc power ;
The LM741 positive power port connects the positive dc power and a ac power supply which amplitude is 1.

Hello, I have try the simulation, but...
why the curve is invert ???
How can i fix this problem ??? thanks !

 

[Saeedafzalkhan]

lm741 scheme

Checkout This LInk:
h**p://focus.ti.com/lit/an/sloa011/sloa011.pdf

 

[rfic]

cmrr and psrr

www.aicdesign.org

 

[duron999]

simulate cmrr source

www.aicdesign.org

i try to give a positive feedback, but the result is not correct too....

 

[mayluli1981]

how is signal supply voltage op with PSRR+ or PSRR- testing ?