Electronics > Beginners
Measuring transconductance of any circuit
Wimberleytech:
--- Quote from: promach on December 16, 2018, 01:12:17 pm ---
--- Quote --- That is why my method to calculate Gm has on reactive components.
--- End quote ---
Investigate the Gm blocks separately as suggested by the forum title itself
This is my personal opinion as of now but please bear in mind that I could be wrong as well
--- End quote ---
That is perfectly fine to do them separately. What I have shown you, is a method to simulate and find the Gm of any block. I have already shown you an example using the inverter. Here is the diff stage.
promach:
Why use voltage source for E1 (or E2) negative input terminal ?
Why use current source for E1 (or E2) positive input terminal ?
Wimberleytech:
--- Quote from: promach on December 16, 2018, 04:55:26 pm ---Why use voltage source for E1 (or E2) negative input terminal ?
Why use current source for E1 (or E2) positive input terminal ?
--- End quote ---
Does this help?
promach:
Sorry for my post here, but it "seems" like you are still not measuring the overall transconductance of a circuit block separately (and independently) without using any feedback circuit (which is the opamp or E1/E2 in your previous post).
I understand that you need to set up the DC operating point from the "feedback" test circuit to emulate the actual gyrator, but if that is the case , you "seems" to miss out the capacitor.
Please correct me if I am wrong in any ways.
Wimberleytech:
--- Quote from: promach on December 17, 2018, 01:27:29 am ---Sorry for my post here, but it "seems" like you are still not measuring the overall transconductance of a circuit block separately (and independently) without using any feedback circuit (which is the opamp or E1/E2 in your previous post).
I understand that you need to set up the DC operating point from the "feedback" test circuit to emulate the actual gyrator, but if that is the case , you "seems" to miss out the capacitor.
Please correct me if I am wrong in any ways.
--- End quote ---
I set up a Gm analysis test for EACH block (the inverter and the diffamp). Your gyrator analysis requires these two Gms. NO CAPACITOR. The gyrator macro block has the capacitor. The equations call out Gm1 and Gm2 and a capacitor, CL.
Gm1 does not depend on CL
Gm2 does not depend on CL
The gyrator which includes Gm1 and Gm2 and CL certainly depends on CL.
The feedback circuit I am using is a TEST CIRCUIT. It is simply measuring the GM of the block (DUT) it is testing. It has NOTHING to do with the gyrator function itself. It is exactly the same as you measuring a resistor with a DVM so that you know what its value is to be used in another circuit. the DVM is not the final circuit...it is the TEST circuit. The final circuit is where the resistor is placed.
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