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Electronic Circuits II > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

Voltages measured with respect to ground

A

Single-ended signals

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2
Q

Consists of two single-ended signals carries over two wires, with two components beginning from the same dc (common-mode) level and changing by equal and opposite amounts

A

Differential signal

More immune to common-mode noise

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3
Q

A differential pair consists of:

A

Two identical transistors, a tail current, two identical loads

P acts as virtual ground

Active mode - making sure input is in signal range and not too large

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4
Q

The circuit “rejects” input CM changes

A

Transistor currents in differential pair remain constant as the input CM level changes

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5
Q

The transistor currents change in opposite directions if

A

A differential input is applied

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6
Q

For small, differential changes at the input, the tail node voltage of a differential pair

A

Remains constant - considered a virtual ground node

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7
Q

Bipolar differential pairs exhibit

A

A hyperbolic tangent input/output characteristic

Tail current can be mostly sorted to one side with a differential input of 4Vt

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8
Q

Small signal operation of differential pair

A

Input differential swing of a bipolar differential pair must remain below roughly Vt

Can be decomposed into two half circuits, each of which is simply a common-emitter stage

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9
Q

MOS differential pairs can steer the tail current with a differential input equal to

A

Sqrt(2) times larger than the equilibrium overdrive of each transistor

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10
Q

MOS differential pairs can provide

A

Linear characteristics depending on the choice of the device dimensions

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11
Q

In the presence of asymmetries and a finite tail current source impedance,

A

A fraction of the input CM change appears as a differential component at the output, corrupting the desired signal

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12
Q

Gain seen by the CM change normalized to the gain seen by the desired signal is

A

Common-mode rejection ratio

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13
Q

Differential pair with active load

A

Replace loads of a differential pair with a current mirror so as to provide a single-ended output while maintaining the original gain

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14
Q

Single ended amps

A

Amplify errors - ripples in VCC

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15
Q

Differential mode

A

2 times the input

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16
Q

Differential amp gain

A

Has differential mode gain and common mode gain

We want max differential mode gain and zero common mode gain to reject common mode signal

17
Q

Vin1»Vin2

A

Q2 almost off (Ve > Vb so current decreases)

All current steers towards Q1

Vout2 = VCC

18
Q

Tail current

A

Guarantees constant collector currents and rejection of the input CM level

19
Q

Telescopic cascode

A

Cascode DX amp loaded with cascode current source

20
Q

Common mode rejection

A

First non-ideality is due to the finite impedance of tail current source (causes change to output)

Short output terminals

2gm

Vp increases

21
Q

Ree = infinity

A

Noise would not show up on outputs

22
Q

Ree < infinity

A

Each input sees noise but differential one doesn’t

Noise will not impact differential output as long as circuit is symmetrical

Single ended output affected

23
Q

Difference in Rd (or Rc) makes CM gain visible in differential output if

A

Ree/Rss = infinity

24
Q

In order for output to be corrupted

A

Tail current source must have finite impedance

Resistor mismatch

25
Q

Differential pair with active load

A

Op-amps have differential input, single ended output

26
Q

Differential to single ended conversion

A

Symmetric differential pair with current mirror

Achieve single ended output without sacrificing gain

Twice Vout

27
Q

Positive feedback

A

Makes input larger

System unstable

28
Q

Negative feedback

A

Makes input smaller

Virtual ground only true with negative feedback

29
Q

CE

A

In - base

Out - collector

30
Q

CB

A

In - emitter

Out - collector

31
Q

CC or emitter Follower

A

In - Base

Out - emitter

Electronic Circuits II (6 decks)

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