Data Sheet

ADA4610-2

Rev. A | Page 15 of 20

APPLICATIONS INFORMATION

COMPARATOR OPERATION

Although op amps are quite different from comparators,

occasionally an unused section of a dual or a quad op amp may

be used as a comparator; however, this is not recommended for

any rail-to-rail output op amp. For rail-to-rail output op amps,

the output stage is generally a ratioed current mirror with bipolar

or MOSFET transistors. With the part operating open loop, the

second stage increases the current drive to the ratioed mirror to

close the loop. However, the second stage cannot close the loop,

which results in an increase in supply current. With the op amp

configured as a comparator, the supply current can be signifi-

cantly higher (see Figure 45). Configuring an unused section as

a voltage follower with the noninverting input connected to a

voltage within the input voltage range is recommended. The

ADA4610-2 has a unique output stage design that reduces the

excess supply current, but does not entirely eliminate this effect

when the op amp is operating open loop.

8

7

6

5

4

3

2

1

0

0

4

8

12

16

20

24

28

32

SUPPLY VOLTAGE (V)

FOLLOWER

Figure 45. Supply Current vs. Supply Voltage

1+

+ –

D31

Q28

Q27

Q15

Q14

Q13

Q17

Q16

Q23

Q29

Q30

J1

J2

Q9

Q5

Q4

Q8

Q1

Q6

Q7

Q25

Q24

Q18

Q12

C2

C1

C3

DE1

C4

A2

A1

R16

R7

R6

R3

R5

R2

R10

R11

RC4

D26

R16

DE5

DE6

DE3

DE2

DE4

Figure 46. Simplified Schematic