MC3458D View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC3458D

Dual, Low Power Operational Amplifiers

Motorola => Freescale 

MC3458 MC3358

Representative Schematic Diagram

(1/2 of Circuit Shown)

Q19

Q18

Bias Circuitry

Common to Both

Output

Amplifiers

VCC

Q27

Q20

Q17

Q16

Q23

+

Q22

Inputs

–

Q21

Q2

Q3

5.0 pF

Q24

Q25

Q6

40 k

31 k

Q1

Q15

2.0 k

Q9

37k

Q13 25

Q11

Q12

Q5

Q7

Q10

Q4

60 k

Q8

Q29

Q28

Q30

2.4 k

VEE (Gnd)

Inverter Pulse Response

20 µs/DIV

CIRCUIT DESCRIPTION

The MC3458/3358 is made using two internally

compensated, two–stage operational amplifiers. The first

stage of each consists of differential input devices Q24 and

Q22 with input buffer transistors Q25 and Q21 and the

differential to single ended converter Q3 and Q4. The first

stage performs not only the first stage gain function but also

performs the level shifting and transconductance reduction

functions. By reducing the transconductance, a smaller

compensation capacitor (only 5.0 pF) can be employed, thus

saving chip area. The transconductance reduction is

accomplished by splitting the collectors of Q24 and Q22.

Another feature of this input stage is that the input Common

Mode range can include the negative supply or ground, in

single supply operation, without saturating either the input

devices or the differential to single–ended converter. The

second stage consists of a standard current source load

amplifier stage.

The output stage is unique because it allows the output to

swing to ground in single supply operation and yet does not

exhibit any crossover distortion in split supply operation. This

is possible because Class AB operation is utilized.

Each amplifier is biased from an internal voltage regulator

which has a low temperature coefficient thus giving each

amplifier good temperature characteristics as well as

excellent power supply rejection.

4

MOTOROLA ANALOG IC DEVICE DATA

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