Chapter 2 Flashcards
What are the internal stages of an op amp?
- Differential Amp Stage
- High-gain Amp Stage
- Output Amp Stage
What is an op amp?
A DC coupled high-gain electronic voltage amplifier with a differential
input and, usually, a single-ended output
What are the 5 terminals of op amp?
*V+: non-inverting input
*V−: inverting input
*Vout: output
*VS+: positive power supply
*VS−: negative power supply
What is a Dual-In-Line or S.O. package?
The 741 IC that we used in the lab. (8 pins and rectangular shape)
What is a Ceramic Flatpak?
The square shaped 741 IC and 8 pins.
What is Metal Can Package?
The circle shaped 741 IC and 8 pins.
What is the inverting input?
The negative terminal.
What is the noninverting input?
The positive terminal.
What is the minimum number of terminals required by a single op amp?
5
What is the minimum number of terminals required on an IC package containing four op amps (called a quad op amp)?
14
What is the characteristic of a ideal op amp?
- v3=A(v2 – v1)
- Infinite input impedance
- Zero output impedance
- Zero common-mode gain (Acm = 0)
- Infinite common-mode rejection
- Infinite open-loop gain A
- Infinite bandwidth
Basic (Closed Loop) Op amp Circuits
– Inverting amplifier
– Generalized impedances
* Inverting integrator
* Inverting differentiator
– Weighted summer
– Non-inverting amplifier
– Voltage buffer
– Difference amplifier
– Instrumentation amplifier
What is the differential input signal (Vid) ?
The difference between the
two input signals v1 and v2 (v2 - v1)
What is the common-mode input signal (Vicm) ?
The average of the
two input signals v1 and v2 ((v2 + v1) / 2)
What is v1?
Vicm - (Vd/2)
What is v2?
Vicm + (Vd/2)
Which terminals are grounded and connected to the source in an inverting amp?
Negative Terminal Connected to Source
Positive Terminal Grounded
Which terminals are grounded and connected to the source in an non-inverting amp?
Positive Terminal Connected to Source
Negative Terminal Grounded
What is the application of a weighted summer amp?
Application: audio systems for mixing signals originating from different musical instruments
What is a Buffer Amp?
Output voltage is equal in both magnitude and phase to the input source
Why are the buffer amps useful?
The input impedance of the op-amp is very high, giving effective isolation of the output from the signal source.
What is the effect of buffer amps?
When very high input impedance, very little current is drawn from the circuit, avoiding “loading” effects
CMRR
Common Mode Rejection Ratio
Common-Mode Gain
Ad = Vo / Vcm
Differential Gain
Ad = Vo / Vd
Instrumentation Amp
- Two buffers at the input terminals.
- W/ additional voltage gain.
- W/ “floating” configuration.
- Very high input resistance.
- High differential gain.
- Symmetric gain. (Assuming A1 and A2 match.
Subtracter Vout
V1 - V2
- V1 drives an inverter with a voltage gain of unity, output of first stage –V1.
- Since the gain of each channel is unity, final output voltage equals v1 minus v
Averager Vout
-(V1 + V2 + V3) /3
When all amplified outputs are added, an output is the average of all input
voltages.
Virtual Ground
- Voltage = Zero
- Current does not go through.
Inverting Integrator
- Resistor is connected to negative terminal
- Capacitor is the feedback
Inverting Differentiator
- Capacitor is connected to the negative terminal
- Resistor is the feedback
