JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III INDUSTRIAL ELECTRONICS Previous Question Paper (March - 2024 - R16)

A DC amplifier is required to amplify signals that have zero or very low frequency components, which cannot be processed by conventional AC-coupled amplifiers. Since AC amplifiers use capacitors or transformers that block DC signals, they are unsuitable for applications like instrumentation, medical equipment (e.g., ECG/EEG), and control systems where the signal level or slow-varying DC offset contains critical information that must be preserved and amplified.

The ideal specifications of an operational amplifier (Op-Amp) are as follows:

• Infinite Open-Loop Gain: The gain of the Op-Amp is infinite, ensuring that the output voltage is independent of the load.
• Infinite Input Impedance: The input impedance is infinite, which prevents any current from flowing into the input terminals, thereby avoiding loading effects on the source.
• Zero Output Impedance: The output impedance is zero, allowing the Op-Amp to act as an ideal voltage source that can drive any load without a drop in output voltage.
• Infinite Bandwidth: The Op-Amp can amplify signals of any frequency, from DC to infinite frequency, with constant gain.
• Zero Offset Voltage: When the input voltage difference is zero, the output voltage is exactly zero.
• Infinite Common-Mode Rejection Ratio (CMRR): The Op-Amp completely rejects any common-mode noise or signals present at both inputs.