80- A

m

Current Regulator

80 mA

60 mA

10 mA

10 mA

OUT

GND

IN+

IN−

Epi-FET

Diodes

Resistors

Transistors

COMPONENT COUNT

1

2

1

20

9

TL331, TL331B, TL391B

www.ti.com

SLVS238H – AUGUST 1999 – REVISED MAY 2020

Product Folder Links: TL331 TL331B TL391B

Submit Documentation Feedback

Copyright © 1999–2020, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The TL331 family is a single comparator with the ability to operate up to 36 V on the supply pin. This standard

device has proven ubiquity and versatility across a wide range of applications. This is due to its very wide supply

voltages range (2 V to 36 V), low Iq, and fast response.

enable the comparator to be used in AND functionality.

The TL331B and TL391B are performance upgrades to standard TL331 using the latest process technologies

allowing for lower offset voltages, lower input bias and supply currents and faster response time over an

extended temperature range. The TL331B can drop-in replace the "I" or "K" versions of TL331. The TL391B is an

alternate pinout for replacing competitive devices.

7.2 Functional Block Diagram

Current values shown are nominal.

7.3 Feature Description

TL331 family consists of a PNP Darlington pair input, allowing the device to operate with very high gain and fast

response with minimal input bias current. The input Darlington pair creates a limit on the input common mode

The output consists of an open collector NPN (pull-down or low side) transistor. The output NPN will sink current

when the negative input voltage is higher than the positive input voltage and the offset voltage. The VOL is

current.

7.4 Device Functional Modes

7.4.1 Voltage Comparison

The TL331 operates solely as a voltage comparator, comparing the differential voltage between the positive and

negative pins and outputting a logic low or high impedance (logic high with pull-up) based on the input differential

polarity.