Functional blocks — a typical monolithic operational amplifier includes (at minimum) an input differential amplifier, a high-gain intermediate/voltage amplification stage, and an output buffer/driver. Is this characterization appropriate?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Despite wide variation among families, most general-purpose op-amps share a recognizable internal architecture: a differential input stage for high input impedance and common-mode rejection, one or more high-gain intermediate stages, and an output stage capable of driving loads. Recognizing these blocks helps explain datasheet parameters such as input offset, open-loop gain, slew rate, and output swing.


Given Data / Assumptions:

  • Monolithic op-amp intended for linear amplification from DC into the kHz–MHz range, subject to device limits.
  • Closed-loop operation with negative feedback is typical in application.
  • Additional blocks (bias networks, protection, compensation) may be present but do not change the core three-stage view.


Concept / Approach:
The input differential pair compares the two input voltages and converts their difference into a current/voltage signal while rejecting common-mode components. A high-gain stage (often a Miller-compensated voltage amplifier) provides most of the open-loop gain and sets the dominant pole for stability. The output stage buffers the high-gain node, supplies current, and reduces output impedance, enabling the op-amp to drive external loads and feedback networks robustly.


Step-by-Step Solution:

1) Identify the differential input pair and associated current mirrors (sets input behavior and CMRR).2) Note the high-gain intermediate amplifier with compensation capacitor (sets A_OL and bandwidth).3) Recognize the output emitter follower or push-pull stage (sets drive and swing limits).4) Map datasheet specs (A_OL, SR, Rout) back to these stages for intuition.


Verification / Alternative check:
Block diagrams in op-amp datasheets routinely depict this three-stage arrangement; application notes explain how each stage contributes to closed-loop behavior and stability.


Why Other Options Are Wrong:

“Incorrect” contradicts common architectures.Limiting to discrete or rail-to-rail devices ignores that this structure spans many technologies.Package type does not determine internal stage topology.


Common Pitfalls:
Assuming the presence of AC coupling between stages; forgetting that compensation and protection circuitry are support functions, not replacements for the core stages.


Final Answer:
Correct

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