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

## 1. Opamp model

Figure 1. Discrete opamp schematic
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!