Due Wednesday Feb 20 at the start of class
1. Draw the smallsignal equivalent circuit

Replace each transistor in Figure 2, “Folded cascode amplifier — AC equivalent circuit” with its smallsignal equivalent circuit.
(this was done inclass Monday)
2. Linear circuit analysis
Consider the three capacitors Cin
, Cb
, and Cout
as “BFC’s” — i.e. large enough to be effectively short circuits at all signal frequencies.
It will be acceptable to ignore \(r_o\) (consider an open circuit) for Q2
, it has little numerical influence in this circuit.
Use this smallsignal equivalent circuit to find symbolic solutions for:

\(v_2\) as a function of \(v_1\)

\(v_{out}\) as a function of \(v_2\)

\(v_{out} / v_{in}\)

\(v_{out} / v_{s}\)
Use the resistor values determined from Homework 07 to compute the transistor smallsignal parameters \(r_\pi\), \(r_o\), and \(g_m\) for each transistor with the help of
Tour Book Table 4. Smallsignal parameters
and
Tour Book Table 2. Transistor parameter definitions
.
Then compute the overall amplifier’s smallsignal input and output resistances and opencircuit voltage gain.
Remember that the definition of A_{v0} is the voltage gain from \(v_{in}\) (not Vs
!) to \(v_{out}\) with the load disconnected.
For help determining where, exactly, the amplifier input and outputs are, consider capacitors Cin
and Cout
as connecting the signal source and load to the amplifier’s proper input and output, respectively.
Device  Value (units) 

R_{in} 

R_{out} 

A_{v0} 
You can crosscheck these values by computing them via a different route by using the “table technique” with Tour Book Table 6. Bipolar transistor amplifier types. They should also match your measurement results for Lab 3B.