LOAD

V

SUPPLY

1

C

FILT

V+

R

1

R

L

R

1

5 kW

R

R

SHUNT

FILTER

<<

R

100

FILT <

W

R

100

FILT <

W

V

IN+

f

-3dB

2 (2 R

) C

p

FILT

FILT

f

=

-3dB

V

IN-

+5 V

5 kW

OUT

INA193A

INA193A-EP

www.ti.com

SBOS400A – MAY 2007 – REVISED SEPTEMBER 2013

Figure 5. Input Filter (Gain Error – 15% to –2.2%)

Inside the INA193A

The INA193A uses a new, unique internal circuit topology that provides common-mode range extending from –16

V to 80 V while operating from a single power supply. The common-mode rejection in a classic instrumentation

amp approach is limited by the requirement for accurate resistor matching. By converting the induced input

voltage to a current, the INA193A provides common-mode rejection that is no longer a function of closely

matched resistor values, providing the enhanced performance necessary for such a wide common-mode range.

A simplified diagram (shown in Figure 6) shows the basic circuit function. When the common-mode voltage is

positive, amplifier A2 is active.

The differential input voltage, (VIN+) – (VIN–) applied across RS, is converted to a current through a resistor. This

current is converted back to a voltage through RL, and then amplified by the output buffer amplifier. When the

common-mode voltage is negative, amplifier A1 is active. The differential input voltage, (VIN+) – (VIN–) applied

across RS, is converted to a current through a resistor. This current is sourced from a precision current mirror

whose output is directed into RL converting the signal back into a voltage and amplified by the output buffer

amplifier. Patent-pending circuit architecture ensures smooth device operation, even during the transition period

where both amplifiers A1 and A2 are active.

Copyright © 2007–2013, Texas Instruments Incorporated

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