EECS 141  Hardware Lab No. 1
CMOS INVERTER AND GATES

I. OBJECTIVE
The objective of this experiment is to determine the Voltage Transfer Characteristic (VTC) of a CMOS inverter and to observe its characteristics in loaded conditions.

II. VOLTAGE TRANSFER CHARACTERISTIC

(1) Calculate several points, including VOH , VIH , VOL , and VIL on the VTC, for the CMOS inverter shown in Figure 1. Used the following transistor data:

Table 1: Transistor Data 

Parameter

 Value
Cox 35 nF/cm2
2f 0.6 V
n 580 cm2/Vs
p 232 cm2/Vs
0.0025
source and drain junctions abrupt
HINT For simplicity in hand calculations, take output voltage as the independent parameter; calculate ID and input voltage from it.
 
(2) Wire up the CMOS inverter shown in Figure 1 and observe its VTC. Compare with your calculated result from Step (1).

III. GATE CONNECTION--RING OSCILLATOR

(1) Wire up 5 CMOS gates to form a ring oscillator as shown in Figure 2. Use the oscilloscope to measure its oscillation frequency at supply voltages of 4, 5, 7, and 10 V. From your results, calculate the average propagation delay per gate at each of these voltages.

(2) Load each of the five output nodes of your ring oscillator with the same capacitance value of 50 pF. Measure the oscillation frequency at VDD = 10V. Assume that propagation delay is a linear function of total capacitance at the output node of a gate (a good assumption), and calculate the approximate equivalent capacitance (due to internal nodes, package, and external wiring) present at the output of each gate with no additional loading capacitors added.