🔍 Key Concepts

• Operational amplifier (op-amp) internal blocks: differential amplifier, voltage amplifier, output amplifier • The role of the input stage of an op-amp in setting input impedance • How op-amps interface with signal sources vs. loads (inputs vs. outputs)

💭 Think About

• Look at block A: Which part of the op-amp first receives the inverting and non‑inverting inputs, and what must its impedance be so it does NOT load the previous circuit? • Think about which stage of an op-amp is mainly responsible for driving the external circuit at the output, and which stage is instead responsible for sensing a small difference between the two inputs. • For a measuring/sensing stage, would you generally want current to flow into it (low impedance) or almost no current to flow (high impedance)?

✅ Before You Answer

• Identify that the differential amplifier is the input stage that both inverting and non‑inverting inputs feed into in figure A. • Recall that high input impedance means very little input current; low input impedance means the source is heavily loaded. • Before choosing, separate in your mind: input characteristics (seen by the source) vs. output characteristics (seen by the load).