Design a circuit which gives the output as multiply by 4 without using any gates?

To design a circuit that multiplies an input signal by 4 without using gates, you can use an analog approach with an operational amplifier (op-amp) configured as a non-inverting amplifier with a gain of 4. This can be achieved by using resistors R1 and R2 such that the gain is defined by the formula ( \text{Gain} = 1 + \frac{R2}{R1} ). By selecting R2 to be four times the value of R1, the circuit will multiply the input voltage by 4. Additionally, you can implement a digital approach using a microcontroller that reads the input value and outputs the result multiplied by 4 through its digital output pins.