Answer Posted / dlhylton

An op amp has high input impedance to prevent loading. When
the impedance is very high, the current that the op amp
draws is very low.

Op amps also have high input impedance because it's a
voltage gain device. In order for the op amp to amplify the
voltage, the voltage signal must drop fully across. And for
this to happen, the op amp must have high input impedance,
v=ir. The greater the impedance, the greater the voltage
drop.

Check out:
http://www.learningaboutelectronics.com/Articles/Why-does-
an-op-amp-need-a-high-input-impedance-and-a-low-output-
impedance

for full explanation

Tell me can a gas be used for conducting current?

906

---

What are the different types of communications?

1084

---

How output frequency is varied in case of a thyristor?

1187

---

Explain what is the tri state of a signal?

1107

---

What is conductance? How is it measured?

1254

---

why the exchang voltge is in minus polarty i.e -48 instead of +48

2056

---

what current is transistor biased?

1019

---

Is reverse saturation current of a diode is independent of reverse bias voltage?

1092

---

In the case of baseband signaling, the received waveforms are already in a pulse-like form. Why then, is a demodulator (receiving filter) needed to recover the pulse waveform?

2576

---

Describe the difference between p-type and n-type semiconductor materials.

1165

---

I have an instrument that involves an electronic circuit. In circuit there is a PTC B754 (having operating voltage 230V). PTC is already damaged and same PTC is not available in market. Now what can i do to solve that problem.

2622

---

what is ISDN 1:2or 1:8 ? what is bandwidth allocation? how to the design small network with 4 router?

2113

---

Hi, sir. im in need of placement questions to train myself as a professional engineer. this is my kind request.

1826

---

Define what is demodulation?

1257

---

in govt polytechnic lecturers tell me what is the expected cut off for ece after the interview list announced

2025

---