VO1 V+
13
G • VD
2
VCM
–
1
PGA204
PGA205
4
Over-Voltage
Protection
Feedback
12
A1
25kΩ
25kΩ
VD
2
16
A1
A0
Digitally Selected
Feedback Network
A3
VO
15
14
11
10
Digital
Ground
VD
2
A2
Ref
5
Over-Voltage
Protection
VCM
25kΩ
25kΩ
9
8
G • VD
VCM
+
VO2
V–
2
FIGURE 5. Voltage Swing of A1 and A2.
Input-overload often produces an output voltage that appears
normal. For example, consider an input voltage of +20V on
one input and +40V on the other input will obviously exceed
the linear common-mode range of both input amplifiers.
Since both input amplifiers are saturated to the nearly the
same output voltage limit, the difference voltage measured
by the output amplifier will be near zero. The output of the
PGA204/205 will be near 0V even though both inputs are
overloaded.
V+
47kΩ
47kΩ
–
VIN
A1
A0
PGA204
PGA205
+
VIN
INPUT PROTECTION
The inputs of the PGA204/205 are individually protected for
voltages up to ±40V. For example, a condition of –40V on
one input and +40V on the other input will not cause
damage. Internal circuitry on each input provides low series
impedance under normal signal conditions. To provide
equivalent protection, series input resistors would contribute
excessive noise. If the input is overloaded, the protection
circuitry limits the input current to a safe value (approxi-
mately 1.5mA). The typical performance curve “Input Bias
Current vs Common-Mode Input Voltage” shows this input
current limit behavior. The inputs are protected even if no
power supply voltage is present.
B
C
X
A
D
D1, D2: IN4148, IN914, etc.
GAIN
PGA204 PGA205
SWITCH
POSITION
A
B
C
D
1
10
100
1000
1
2
4
8
FIGURE 6. Switch-Selected PGIA.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
®
13
PGA204/205
BB [ BURR-BROWN CORPORATION ]
