Inverter characteristics

Goals: You'll be using inverters in a CD4069 CMOS inverter chip as transconductors(VCCS). In this experiment you'll measure the large and small signal characteristics of this transconductor. In all experiments, remember to disable the unused inverters. Do all steps for V_cc=5V, 6V, and 9V.

Determine I_out versus V_in of the transconductor using the circuit above. Vary the input voltage from 0 to Vcc. You can use a separate power supply for generating the variable bias voltages or a resistive voltage divider(say, a chain of 16 identical resistors from Vcc to ground). What is the self bias voltage V_M of the inverter? Estimate the transconductance at V_M.

Determine V_out versus V_in of the transconductor(with an open circuit load as shown above). Take more points in the high gain region for accurate determination of gain.

Bias an inverter at V_M by shorting its input and output as shown above. What is the small signal resistance looking into this circuit? Measure it by forming a voltage divider with one arm being the small signal resistance as shown in the circuit above. Are the values consistent with the earlier measurements?

From the above measurements, estimate the small signal output resistance Rout of the transconductor, and threshold voltages and current factors of nMOS and pMOS transistors.

You'll need the measured parameter values for subsequent experiments(g_m,inv, r_out,inv, V_Tp, V_Tn, μ_pC_ox, μ_nC_ox). So keep a record of them.

Applications: Transconductors are building blocks of practically all analog ICs albeit with numerous other topologies besides the CMOS inverter. Regardless of the topology, you'll need to do similar simulations/measurements as the ones here to ascertain their parameters.