Generic 741 Switched Non-Inverting Amplifier

This circuit uses a Generic 741 operational amplifier as a non-inverting gain stage. The input sine wave passes through SW1 into the non-inverting input, while RF and RG set the closed-loop gain. The output drives an LED load so the amplified signal can be inspected as both a waveform and load current.

Suggested Applications

• Amplifying a small AC control or sensor signal before driving a visible indicator.
• Demonstrating how a non-inverting op amp stage responds when an input path is opened or closed.
• Comparing input voltage, output voltage, and LED/load current in a practical amplifier stage.

Featured Component

The Generic 741 Op Amp is a classic general-purpose operational amplifier model. In this circuit, it demonstrates closed-loop non-inverting gain using split +/-15 V supplies and a feedback divider.

Design Context

RF is 9 kOhm from the output to the inverting input, and RG is 1 kOhm from the inverting input to ground. The ideal non-inverting gain is 1 + RF/RG = 10 V/V. The input source is a 500 mV sine wave, SW1 controls whether that signal reaches the amplifier input, and the output drives a green LED through a 100 ohm load resistor.

The VIN and VOUT probes show the applied input and amplified output. The current probe in the LED branch shows how output swing translates into load current.

Expected Behavior

With SW1 closed, VOUT should follow VIN with approximately 10x non-inverting gain while the 741 remains inside its supply and output-current limits. The LED branch conducts when the output voltage is high enough to forward-bias the LED and drive current through RL.

With SW1 open, the input path is interrupted, so the output should no longer track the sine-wave source in the same way.

Suggested Experiments

Toggle SW1, change RF or RG to adjust gain, increase the input amplitude to explore output clipping, or change RL to see how the LED load current affects the output waveform.