EE 308 Quiz 2 StuDie

MOSFET-based differential pair has tail current of 100µA; the gate overdrive of each device is 250mV. The transconductance, that relates id to vin(dm), has this approximate value:

0.2 mA/V -betty and Chloe

To construct 'Sziklai pair' these type of devices are needed. Mark all that apply.

1 NPN, 1 PNP

To construct a 'Darlington pair' these type of devices are needed. Mark all that apply:

2 transistors of the same polarity (2 NPN or 2 PNP)

The differential-input linear range of a BJT differential pair is approximately that many mili-volts:

2*Vt = 50mV (Lecture 14, slide 8)

A push-pull amplifier uses one npn and one pnp. The dead zone of this amplifier is approximately that many mili-volts:

2VBE = 1.4 V = 1400 mV

The output resistance of a simple current mirror is 150kΩ. Two resistors of equal value are inserted in the emitters. If the voltage drop over these resistors is 75mV, the output resistance of the modified topology is approximately:

600 kohm

CC amplifier drives 10kΩ and exhibits input resistance of 500 kΩ. If a load of 15kΩ is presented, the input resistance of this same CC circuit will become approximately:

750kohm

An op-amp with GBW of 2MHz implements a non-inverting amplifier with gain of 25 mV/mV. The 3-dB corner frequency of this amplifier is approximately that many kHz:

80 kHz (GBW = gain*f3db from Lecture 17 pages 3 and 4)

This single-transistor amplifier has Current Gain of approximately unity:

CB

These single-transistor amplifiers have large (compared to 1/gm) output resistance:

CB and CE

This single-transistor amplifier has Voltage Gain of approximately unity:

CC

These single-transistor amplifiers have large (compared to 1/gm) input resistance:

CC and CE

This single-transistor amplifier is best characterized as a transconductor:

CE

These single-transistor amplifiers must be cascaded to produce a circuit that behaves as a Voltage-Controlled-Voltage-Source:

CE-CC

To create differential-input transconductor these type of circuits are needed:

Current Mirror

A CMRR can be defined for this type of an amplifier:

Diff pair Amplifier

These are (some) of the similarities between CE amplifier and CB amplifier:

High voltage gain, collector is output, rout=rc, large rout

A 2-stage (Miller) integrator is constructed using: actively-loaded BJT diff. pair with a tail current of 25 µA, a capacitor with value 50pF, and a CE stage. The frequency of the RHP zero is 10-times larger than the unity-gain frequency of the integrator. The bias current of the CE stage is approximately that many µA:

Ibias = 125uA

The so-called coupling and by-pass capacitors determine this frequency:

Lower 3dB corner frequency (Lec 13, Slide 2)

This amplifier type might experience cross-over distortion:

Push pull amplifiers

An op-amp uses two-stage (Miller) integrator. The integrator consists of an actively-loaded BJT diff. pair with a tail current of 25 µA, capacitor with value 50pF, and a CE stage. The slew rate of this op-amp is no larger than:

SR = Itail/C = 25 uA/ 50 pF = 0.5 V / usec

The advantage of a push-pull CC over a 'regular' CC is:

There is no limit to the amount of current the push-pull can source or sink. Additionally, there is less DC current than a "regular" CC. (lecture 12 slide 9)

A transconductor is another "name" for this type of a dependent source:

VCCS

The load of a CC amplifier is 3 kΩ. If the biased current is 1mA, the maximum output swing (with no clipping) is:

Vout = 3V

Gm-C integrator is constructed using actively-loaded BJT diff. pair with a tail current of 25 µA and capacitor with value 50pF. The unity-gain frequency of this integrator is approximately that many kHz:

f = gm/(2piC) = ITAIL/2VT(2piC) = 1,530 kHz

It is claimed that an amplifier behaves as a VCVS. This therefore must be true regarding its input and output impedances:

high input impedance, low output impedance

The load of a CC amplifier is 10 kΩ (>> 1/gm). If the β of the BJT is 100, then the input resistance of the CC circuit must be on the order of:

rin = 1Mohm

The 'small-signal' behavior of a BJT in forward-active, can be characterized by the following resistive quantities: rπ, ro and 1/gm. For any practical device, this one is the largest:

ro

CE amplifier has gm(eff) of 20 mA/V and β of the BJT is 50. The amplifier input resistance is no larger than:

rpi = 2.5kohm

A high-gain amplifier consists of two CE stages connected in a cascade - the output of the first feeds the input of the second. Which of these CE stages is more likely to feature emitter degeneration?

second stage