Due Monday 2018-04-16 at the start of class.

1. Opamp model

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Figure 1. Discrete opamp schematic
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Figure 2. Small-signal opamp model

Find the numerical values of the small-signal parameters Gm1, R1, Gm2, and R2 shown in Small-signal opamp model that correspond to your discrete opamp of Discrete opamp schematic.

Draw the small-signal model of the schematic.

  • The third stage, the emitter-follower is removed from the small-signal model.

  • The output of the model \(v_o\) and node D6 corresponds to node number 4 in the schematic.

  • For the purposes of this analysis, make set the value of schematic resistor R2 to zero.

  • Since this is a differential input situation, use the “differential mode half-circuit” technique to deal with the input differential pair. Node 3 will therefore be grounded.

  • It is easy to find the Gm's if you find the short-circuit current thru a wire from node 2 to GND or node 4 to GND.

To get a start on the next homework, build both the transistor-level schematic and the small-signal model in LTspice. Monday will have a few techniques for simulating the open-loop parameters of opamps.

2. Notes

As always, ask questions over the Slack #electronics channel.

Hand in your work on ENGINEERING PAPER:[1]

  • One side of writing per page.

  • One column of intermixed schematic, math, and text.

  • Near-zero cross-outs or erase marks. (you have plenty of paper!)[2]


1. I will hand your paper back without grading for you to actually re-write!
2. See Prof. White if you didn’t receive your complementary pad of engineering paper.