Datasheet

10PGA204/205
®
TYPICAL PERFORMANCE CURVES (CONT)
At T
A
= +25°C, and V
S
= ±15V, unless otherwise noted.
NOISE, 0.1 TO 10Hz, G = 1
1s/Div
0.5µV/Div
0.2µV/Div
1s/Div
INPUT-REFERRED NOISE,
0.1 TO 10Hz, G = 1000
FIGURE 1. Basic Connections.
APPLICATION INFORMATION
Figure 1 shows the basic connections required for operation
of the PGA204/205. Applications with noisy or high imped-
ance power supplies may require decoupling capacitors
close to the device pins as shown.
The output is referred to the output reference (Ref) terminal
which is normally grounded. This must be a low-impedance
connection to assure good common-mode rejection. A resis-
tance of 5Ω in series with the Ref pin will cause a typical
device to degrade to approximately 80dB CMR (G=1).
The PGA204/205 has an output feedback connection (pin
12). Pin 12 must be connected to the output terminal (pin 11)
for proper operation. The output Feedback connection can
be used to sense the output voltage directly at the load for
best accuracy.
DIGITAL INPUTS
The digital inputs A
0
and A
1
select the gain according to the
logic table in Figure 1. Logic “1” is defined as a voltage
greater than 2V above digital ground potential (pin 14).
Digital ground can be connected to any potential from the
V– power supply to 4V less than V+. Digital ground is
normally connected to ground. The digital inputs interface
directly CMOS and TTL logic components.
Approximately 1µA flows out of the digital input pins when
a logic “0” is applied. Logic input current is nearly zero with
a logic “1” input. A constant current of approximately
A
1
A
2
A
3
12
11
10
25kΩ25kΩ
25kΩ25kΩ
7
5
14
16
4
V
IN
V
IN
PGA204
PGA205
V
O
= G (V
IN
– V
IN
)
V
O
–
+
Over-Voltage
Protection
Over-Voltage
Protection
Feedback
Digitally Selected
Feedback Network
1
V
O1
15
6 9
8
V
O2
V
OS
Adj
+15V
1µF
+15V
1µF
+–
PGA204
V
IN
V
IN
–
+
V
O
A
1
A
0
Sometimes shown in simplified form:
A
1
A
0
PGA205PGA204
GAIN
0
0
1
1
0
1
0
1
1
2
4
8
1
10
100
1000
Ref