Electronics Online

An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. These circuits are usually applied in robotics and various applications to enable DC motors to move forwards and reverse. H bridges are ready as integrated circuits (IC chip – for example: L298N), or can be built from discrete components (transistors).

General
The term H bridge is derived from the typical graphical representation of such a circuit. An H bridge is built with four switches (solid-state or mechanical). When the switches S1 and S4 (based on the first figure) are closed (and S2 and S3 are open) a positive voltage will probably be applied across the motor. By opening S1 and S4 switches and closing S2 and S3 switches, this voltage is reversed, allowing reverse operation of the motor.

The following is about the application of Operational Amplifier (op-amp) as a non-inverting amplifier:

Amplifies a voltage (multiplies by a constant greater than 1)

• Input impedance
  • The input impedance is at least the impedance between non-inverting ( + ) and inverting ( − ) inputs, which is typically 1 MΩ to 10 TΩ, plus the impedance of the path from the inverting ( − ) input to ground (i.e., R₁ in parallel with R₂).
  • Because negative feedback ensures that the non-inverting and inverting inputs match, the input impedance is actually much higher.

This is the simple explanation about Inverting Operational Amplifier (Op-Amp):

An inverting amplifier makes use of negative feedback to invert and amplify a voltage. The R_in,R_f resistor network permits a few of the output signal to be returned towards the input. Because the output is 180° out of phase, this value is properly subtracted from the input, thereby lowering the input into the operational amplifier. This cuts down the overall gain with the amplifier and is dubbed negative feedback.