Negative Feedback - Current Sum--Voltage Sample

106

01:15:50

The goal was a voltage gain of 20 dB over a 50 Ohm load through a 50 Ohm series resistor and an upper cutoff frequency >5MHz. The static current dissipation through the positive rail was also to be kept under 15 mA. 
I greatly appreciate any feedback regarding potential pitfalls or improvements related to the design!

published 8 years ago

crake

8 years ago

Mission accomplished!

Issacsutt

8 years ago

Try replacing the chain of 4 transistors with just a 3v zener diode

Issacsutt

8 years ago

http://everycircuit.com/circuit/5976835212181504

hurz

8 years ago

@Issacsutt, be careful at this place in circuit, you quickly burn the Amp. And think about were you mount the diodes to track temperatur. E.g. bigger amps to put the diodes on the heatsink and compensate the quitesense current. But not to much, cuz after heatup the amp THD might get horrible when the quitesense current drops to much. Everything needs a well fine tuning.

Issacsutt

8 years ago

Okay

zorgrian

8 years ago

Building this circuit to run at 4-5 MHz will reveal unanticipated problems.

larmar

8 years ago

@zorgrian, you’re definitely right about that! It actually worked “better” before adding the Darlington pairs to the AB output. We added the Darlington Pairs to increase poop gain, but I think that probably caused the phase margin to be insufficient for stability. We thought RC lag compensation might solve the issue, but we finished the assignment before we were able to try. What do you think?

larmar

8 years ago

Loop gain* not poop gain haha

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