Use an op amp connected to a two-color LED to display voltage fluctuations

The op amp is connected to an LED to directly display voltage fluctuations

Figure 1 is a Wien bridge oscillation circuit. It has three output voltages-high, low and oscillation. The amplitude of oscillation is determined by the voltage. Use it to drive a bi-color LED to display the high and low thresholds of voltage.

When Vin is higher than the first threshold voltage, the op amp is in a high-voltage output state. When the input is lower than the second voltage threshold, the op amp is in a low-voltage output state. If the input is between high and low values, the output of the op amp oscillates between high and low values.

Using a two-color diode, through the change of voltage, for example, a green light when the voltage is high and a red light when the voltage is low, the oscillation state of the voltage can be visually displayed .