Differential input and single-ended output type amplifier:
Operational amplifiers (op-amps) are electronic devices that amplify the difference between two input voltages. They have various configurations depending on their input and output types. Option 'A' refers to a differential input and single-ended output type amplifier.

Differential Input:
A differential input means that the amplifier has two input terminals, commonly labeled as the non-inverting input (+) and the inverting input (-). The voltage difference between these two input terminals determines the amplifier's output.

Single-Ended Output:
A single-ended output means that the amplifier has only one output terminal, which produces an amplified version of the voltage difference between the input terminals.

Working of Differential Input and Single-Ended Output Amplifier:
1. The differential input stage: The amplifier's input stage consists of a differential pair of transistors. The non-inverting input (+) is connected to the base of one transistor, and the inverting input (-) is connected to the base of the other transistor.
2. Differential amplification: The differential pair amplifies the voltage difference between the two input terminals. The amplified signal appears at the collectors of the transistors.
3. Single-ended output stage: The output stage of the amplifier is designed to convert the differential voltage at the collectors of the transistors into a single-ended output voltage.
4. Voltage amplification: The output stage amplifies the differential voltage and provides a single-ended output voltage that is proportional to the difference between the input voltages.
5. Output coupling: A coupling capacitor is often used to remove any DC component and pass only the AC component of the output voltage.
6. Load resistance: The output voltage is connected to a load resistance, which determines the current flowing through it and the voltage level seen by the load.

Applications:
- Differential input and single-ended output amplifiers are commonly used in instrumentation systems, audio amplifiers, and data acquisition systems.
- They are suitable for applications where the input signal is differential, but the output signal can be single-ended.
- They can be used for amplifying small differential signals and rejecting common-mode noise.
- Single-ended output makes it easier to interface with other circuits or devices that accept single-ended signals.

In conclusion, a differential input and single-ended output type amplifier is a common configuration of operational amplifiers. It amplifies the voltage difference between two input terminals and provides a single-ended output voltage. This configuration is widely used in various applications in electrical engineering.