Student Zone-Activity: Zero Gain Amplifier (MOS)

This event is a continuation of the student zone in November; this time we will introduce the current mirror, whose output can be unaffected by changes in the input current. Therefore, it is helpful to use MOS transistors to study the performance of zero-gain amplifiers from another perspective.

Author: Analog Devices|Doug Mercer, Consulting Researcher Antoniu Miclaus, System Application Engineer

Target

This event is a continuation of the student zone in November; this time we will introduce the current mirror, whose output can be unaffected by changes in the input current. Therefore, it is helpful to use MOS transistors to study the performance of zero-gain amplifiers from another perspective.

Material

► ADALM2000 Active Learning Module
► Solderless breadboard
► A 2.2 kΩ resistor (or other similar value)
► A 168 Ω resistor (connect 100 Ω and 68 Ω resistors in series)
► A small signal NMOS transistor (enhanced mode CD4007 or ZVN2110A)

instruction

Figure 1 shows the schematic diagram of the NMOS zero-gain amplifier.

Student Zone-Activity: Zero Gain Amplifier (MOS)
Figure 1. NMOS zero gain amplifier

Hardware setup

The breadboard connection is shown in Figure 2. The output of the arbitrary waveform generator 1 is connected to one end of the driving resistor R1. The resistor R2 is connected between the gate and the drain of the transistor M1, and the other end of the resistor R1 is also connected to the gate. The source of M1 is grounded; therefore, M1 uses a common source configuration.

Student Zone-Activity: Zero Gain Amplifier (MOS)
Figure 2. NMOS zero-gain amplifier breadboard circuit

Procedure steps

Waveform generator 1 is configured as a 1 kHz triangle wave with a peak-to-peak amplitude of 4 V and an offset of 2 V. Connect oscilloscope channel 1 to Display the output W1 of the AWG. The single-ended input of oscilloscope channel 2 (2+) is used to alternately measure the gate voltage and drain voltage of M1.

Configure the oscilloscope to capture multiple cycles of the measured two signals. Enable the XY function.

Examples of waveform diagrams using an oscilloscope are shown in Figures 3 to 5.

Student Zone-Activity: Zero Gain Amplifier (MOS)
Figure 3. Waveform diagram of oscilloscope VGATE

Student Zone-Activity: Zero Gain Amplifier (MOS)
Figure 4. Waveform diagram of oscilloscope VDRAIN

Student Zone-Activity: Zero Gain Amplifier (MOS)
Figure 5. Example: comparing VGATE and VDRAIN

problem:

► What is the main purpose of using a zero-gain amplifier in circuit design?

You can find the answers to the questions on the student zone blog.

About the Author

Doug Mercer graduated from Rensselaer Polytechnic Institute (RPI) in 1977 with a bachelor’s degree in electrical engineering. Since joining ADI in 1977, he has directly or indirectly contributed more than 30 data converter products and holds 13 patents. He was appointed as an ADI researcher in 1995. In 2009, he transitioned from a full-time job and continued to serve as an ADI consultant as an honorary researcher, writing articles for the “Active Learning Program”. In 2016, he was appointed as the Resident Engineer of the RPI ECSE Department. Contact information:[email protected]

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