These questions are asked in the technical interview conducted in Goodrich, Bangalore for the post of Design Engineer with 2 year experience. As it is for the experienced engineers, we would have to explain as much as possible about the topic. We did not answer the non technical questions here.
A1: Question about previous exp.
A2: Question about currently working project.
[1] Explain the amplifier operation of OP-AMP?The golden rules of OP-AMP are:
1. Vout = A. Delta Vin [ A = Gain, Delta Vin = V+ - V-]
2. V-- < Vout < V++
3. Zout = 0 , Zin+ = Zin- = Infinity
The opamp will work as inverting amplifier and non- inverting amplifier based on the supply applied to its terminals.
Non Inverting Amplifier:
Inverting Amplifier:
[2]Interrupted and Asked to derive the equation...
Current i = (Vin-Vout) / (Rin+Rf)
=( Vin - Vx)/Rin = (Vout - Vx)/Rf
Vx = virtual ground =the node at inverting input terminal =0
[3] Interrupted and asked what is virtual ground?
Explained.
then i = Vin/Rin - Vx/Rin = Vout/Rf- Vout/Rf
Rearranging we will get the final equation.
[4] Explain how transistor acts as a switch?
The areas of operation for a transistor switch are known as the Saturation Region and the Cut-off Region.
This means then that we can ignore the operating Q-point biasing and voltage divider circuitry required for amplification, and use the transistor as a switch by driving it back and forth between its "fully-OFF" (cut-off) and "fully-ON" (saturation) regions as shown below.
A3: Why do you want such a high salary which is well above the market average?
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