As a continuation of the November StudentZone, this activity introduces a current mirror, which has an output that has been desensitized to variations in input current. Therefore, it is helpful to examine the behavior of a zero-gain amplifier from another perspective, using MOS transistors.
- ADALM2000 Active Learning Module
- Solderless breadboard
- One 2.2 kΩ resistor (or any similar value)
- One 168 Ω resistor (use a 100 Ω in series with a 68 Ω)
- One small signal NMOS transistor (enhancement mode CD4007 or ZVN2110A)
The schematic of an NMOS zero-gain amplifier is presented in Figure 1.
The breadboard connections are as shown in Figure 2. The arbitrary waveform generator 1 output drives one end of resistor R1. Resistor R2 is connected between the gate and drain of transistor M1 with the other end of resistor R1 connected to the gate as well. The source of M1 is grounded; thus, M1 is in a common source configuration.
The waveform generator 1 should be configured for a 1 kHz triangle wave with 4 V amplitude peak-to-peak and 2 V offset. Connect Scope Channel 1 to display output W1 of the AWG. The single-ended input of Scope Channel 2 (2+) is used to measure alternately the gate and drain voltage of M1.
Configure the oscilloscope instrument to capture several periods of the two signals measured. Make sure to enable the XY feature.
Plot examples using the oscilloscope are provided in Figure 3 through Figure 5.
- What would be the main purpose of introducing a zero-gain amplifier in your circuit designs?
You can find the answer at the StudentZone blog.