We have collected some animation demonstrations of the circuit and share them with you now.

Gray code counter

Roads are counted in Gray code, a binary counting system where only one digit changes each time the count is updated.

decimal counter

The circuit is a 4-digit decimal counter. It counts up to 9 ( 1001 , binary) and then starts at 0.

7 segment LED decoder

This circuit uses a 7-segment LED display to input a 4-digit binary number and output a decimal number from 0 to 9. If the entered number is greater than 9, it will be blank.

Voltage Controlled Oscillator

This circuit is a voltage controlled oscillator whose output frequency is an oscillator whose output frequency is determined by the control voltage. In this case, a 10Hz sawtooth oscillator provides the control voltage. This causes the frequency to slowly rise until it reaches a maximum value and then falls back to the starting frequency.

The first op amp is an integrator. The voltage divider places the + input at half the control voltage. The op amp tries to keep its inputs at the same voltage, which requires current to flow across the 100k to ensure its voltage drop is half the control voltage.

When the bottom MOSFET is on, the current from 100k flows through the MOSFET. Since a 49.9k resistor has the same voltage drop as a 100k but half the resistance, it must flow twice as much current. The extra current comes from and charges the capacitor, so the first op amp must provide a steadily rising output voltage to supply this current.

When the bottom MOSFET is turned off, the current from the 100k discharges through the capacitor, so the first op amp needs a steady reduced output voltage. The third range shows the output voltage; it looks like a triangle wave.

The second op amp is a Schmitt trigger. It takes a triangle wave as input. When the input voltage rises above the threshold of 3.33 V, it outputs 5 V and the threshold voltage drops to 1.67V. When the input voltage drops to this voltage, the output becomes 0 V and the threshold moves up again. The output is a square wave. It is connected to a MOSFET that allows the integrator to step up or down its output voltage as needed.

gyrator

Inductors can be bulky, bulky, and expensive, so replacing them with inexpensive components is often valuable. At the bottom is the simulated inductor circuit.

Capacitors pass high frequencies (and sudden changes), causing the + input of the op amp to be closer to the input signal. (Since the resistor (20k) is large, there isn't much current going through the capacitor.) The op amp keeps the – input at the same level as the +, allowing less current to flow through the 1k resistor since the voltage is almost the same as the input voltage. This circuit can block high frequencies, such as inductors.

This capacitor blocks low frequencies (and stabilizes voltage), causing the + input of the op amp to be closer to ground. The op amp keeps the – input at the same level as the +, causing more current to flow through the 1k resistor to ground. It passes low frequencies like an inductor.

Tesla Coil

This is the Tesla coil circuit. Transformers step up the input voltage by a factor of 100 to produce high voltages. After a few seconds, the voltage is high enough to ignite the spark plug. Then, the capacitor and the primary coil of the second transformer form a resonant circuit. The secondary transformer coil is connected to the toroid, represented here by capacitance to ground. It also forms a resonant circuit with a resonant frequency of about 200kHz. The energy is gradually transferred from the first circuit to the second circuit, and then the spark gap stops conducting, keeping all the energy in the loop circuit.

Once the spark plug stops conducting, it takes a while for enough voltage to build up to make it fire again. The simulation speed is greatly reduced, so the 200kHz oscillation can be seen. You may need to reload the circuit instead of waiting.

555 Square Wave Oscillator

This is a simple square wave oscillator using a 555 timer chip.

The timing interval begins when the trigger input ("tr") falls below 1/3 V in or 3.33V. When this happens, the 555 output goes high and the 555 waits for the threshold input ("th") to reach 2/3 V in or 6.67V. As the capacitor charges, the threshold input slowly rises until it reaches the required level. Then, the timing interval ends, the output goes low, and the capacitor discharges.

A new timing interval begins when the capacitor discharges enough for the flip-flop to reach 3.33V. The end result is a square wave.

current mirror

This is a current mirror, a device that uses one half of a circuit's current to control the other half. Both halves have the same current. The switch on the left changes the current in the left half, which is mirrored in the right half. The switch on the right causes the resistor to be bypassed, but the current mirror ensures that the current doesn't change.

The emitter-base junction of Q1 acts like a diode. The current through it is set by the resistor network below it. Connecting the base to the collector ensures that the base current can flow so the transistor can remain in active mode. Since Q1's base is connected to Q2 at the same voltage, they are at the same voltage, so the same current must flow through the emitter-base junction of Q2. (It acts like a diode, so the current is determined by the voltage across it.)

The two halves of the circuit have almost the same current flowing through them. The only difference is that the base current from Q1 and Q2 flows through the left half, not the right half. We use high beta transistors in this circuit to keep these base currents as small as possible.

boost circuit

This circuit uses some diodes and capacitors to generate 42V from a 15 V input signal.

memristor

This example shows a memristor. It acts as a resistor, but the resistance changes over time. In this example, use the slider on the right to select the input voltage. Memristors initially have high resistance, but current causes this resistance to decrease over time until it reaches a minimum value. If the input voltage is set to a negative value, the resistance will gradually increase until it reaches a maximum value. A graph of the memristor's voltage, current, and resistance is shown below the circuit.

This example shows the response of a memristor to a sine wave. The graph below the circuit shows the memristor's voltage (green), current (yellow), and resistance (white). A graph of voltage versus current is also shown. Note that voltage and current have a non-linear relationship.