Datasheet

LTC6910-1
LTC6910-2/LTC6910-3
22
6910123fa
+
–
+
–
8
7
6
5
V
–
V
OUT
R4 15.8k
V
–
V
+
V
+
LT1884
C2
1µF
C1
10µF
R1
15.8k
2
7
8
3
V
IN
6
4
5
1
R2
15.8k
0.1µF
GN2 GN1 GN0
0 0 1 GAIN = 1
0 1 0 GAIN = 2
0 1 1 GAIN = 5
1 0 0 GAIN = 10
1 0 1 GAIN = 20
1 1 0 GAIN = 50
1 1 1 GAIN = 100
BW2BW1BW0
BANDWIDTH 1Hz TO 10Hz 0 0 1
BANDWIDTH 1Hz TO 20Hz 0 1 0
BANDWIDTH 1Hz TO 50Hz 0 1 1
BANDWIDTH 1Hz TO 100Hz 1 0 0
BANDWIDTH 1Hz TO 200Hz 1 0 1
BANDWIDTH 1Hz TO 500Hz 1 1 0
BANDWIDTH 1Hz TO 1000Hz 1 1 1
0.1µF 0.1µF
V
+
V
–
1
2
3
4
2
7
8
3
6
4
5
1
0.1µF
0.1µF 0.1µF
V
+
V
–
LTC6910-1
LTC6910-1
R3
15.8k
BANDWIDTH
CONTROL
GAIN
CONTROL
FREQUENCY (Hz)
–60
GAIN (dB)
–50
–30
–20
0
10
1 100 1k 100k
6910 F06b
–70
10
10k
–10
–40
–80
GN2 GN1 GN0 = 001
BW2
1
BW1
0
BW0
0
BW2
0
BW1
0
BW0
1
BW2
1
BW1
1
BW0
1
Gain vs Frequency
Figure 8. Low Noise AC Amplifier with Programmable Gain and Bandwidth
TYPICAL APPLICATIO S
U
Measured frequency responses in Figure 8 with
LTC6910-1 PGAs demonstrate bandwidth settings of 10Hz,
100Hz and 1kHz, with digital codes at the BW inputs of
respectively 001, 100 and 111, and unity gain in each case.
By scaling C2, this circuit can serve other bandwidths,
such as a maximum of 10kHz with 0.1µF using LT1884
(gain-bandwidth product around 1MHz). Noise floor from
internal sources yields an output SNR of 76dB with 10mV
P-
P
input, gain of 100 and 100Hz bandwidth; for 100mV
P-P
input, gain of 10 and 1000Hz bandwidth it is 64dB.