QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 566
DIGITALLY CONTROLLED PROGRAMMABLE GAIN AMPLIFIER
1
LTC6910
DESCRIPTION
Demonstration circuits 566A-A, -B and -C, feature the
easy to use, rail-to-rail input and output LTC6910 se-
ries of Low Noise Programmable Gain Amplifier
(PGA) parts. The inverting gain is set by changing the
positions of three onboard jumpers: G0, G1 and G2 to
set the 3-bit programming code. Demo Circuit 566A-
A is for the LTC6910–1 with gains of 0, 1, 2, 5, 10,
20, 50, 100 V/V. Demo Circuit 566A-B is for the
LTC6910–2 with gains of 1, 2, 4, 8, 16, 32, and 64
V/V. Demo Circuits 566A-C is for the LTC6910–3 with
gains of 1, 2, 3, 4, 5, 6 and 7 V/V.
All three-demo boards have input jumpers to select
between AC or DC coupling of the input, and a jumper
to select operation with a single or dual supply. Typi-
cal applications include data acquisition systems, dy-
namic gain changing, automatic ranging circuits and
automatic gain control. The LTC6910 family can op-
erate from single or split supplies from 2.7V to 10.5V
total between V+ and V-.
Design files for this circuit board are available. Call
the LTC factory.
Table 1.
Performance Summary (TA = 25°C)
PARAMETER CONDITION VALUE
Supply Voltage Range V+ to V– 2.7V to 10.5V
Gain Accuracy Gain Dependent (see Data
Sheet)
Typical
±0.05dB at
Gain = 1
and ±0.4 dB at
Gain = 100
Vs = ±2.5V, VOUT = ±1.4V 12V/µs Slew Rate
Vs = ±5V, VOUT = ±1.4V 16V/µs
FREQUENCY (Hz)
10
GAIN (dB)
30
50
0
20
40
100 10k 100k 1M 10M
6910 G02
–10
1k
GAIN OF 100 (DIGITAL INPUT 111)
GAIN OF 1 (DIGITAL INPUT 001)
GAIN OF 2 (DIGITAL INPUT 010)
GAIN OF 5 (DIGITAL INPUT 011)
GAIN OF 10 (DIGITAL INPUT 100)
GAIN OF 20 (DIGITAL INPUT 101)
GAIN OF 50 (DIGITAL INPUT 110)
VS = 10V, VIN = 5mVRMS
Figure 1.
LTC6910-1 Frequency Re-
sponse
FREQUENCY (Hz)
10
GAIN (dB)
30
50
0
20
40
100 1k 100k 1M 10M
69102 TA02
–10
10k
VS = ±5V
VIN = 10mVRMS
GAIN OF 64
GAIN OF 32
GAIN OF 16
GAIN OF 4
GAIN OF 8
GAIN OF 2
GAIN OF 1
Figure 2.
LTC6910-2 Frequency Re-
sponse
FREQUENCY (Hz)
0
GAIN (dB)
10
20
–5
5
15
1k100 100k 1M 10M
69103 TA02
–10
10k
GAIN OF 7 GAIN OF 6
GAIN OF 5
GAIN OF 4
GAIN OF 3
GAIN OF 2
GAIN OF 1
V
S
= ±5V
V
IN
= 10mV
RMS
Figure 3.
LTC6910-3 Frequency Re-
sponse
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 566
DIGITALLY CONTROLLED PROGRAMMABLE GAIN AMPLIFIER
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Figure 4.
Proper Measurement Equipment Setup
QUICK START PROCEDURE
The 566 family of Demonstration boards allow for
easy evaluation of the performance of the LTC6910
series of PGAs. Refer to Figure 4 for proper meas-
urement equipment setup and follow the procedure
given below:
1.
Place jumpers in the following positions:
SINGLE for Single Supply
DUAL for Dual Supply
DC for DC Coupling
AC for AC Coupling
f–3dB = 1/(2πC7RINPUT)
C7 = 10µF, RINPUT is the nominal input im-
pedance and depends on the gain setting,
see Table 2, 3, or 4.
The jumper settings given in this procedure set the
gain to a value of –1 (the LTC6910-X is an inverting
amplifier), for other gain values refer to Gain Table
2, 3 or 4 which matches the Demo Circuit, 566-A, -
B, or -C. To set the gain to a value of –1 set:
G0: Set to Logic 1
G1: Set to Logic 0
G2: Set to Logic 0
2.
With the power off, connect the input power supply
to V+, V- and AGND as required.
NOTE:
Make sure that the input voltage does not
exceed 11V total between V+ and V–.
3.
Set a function generator to output a 1kHz 1VP–P
signal.
4.
Set the input jumper to give the desired input cou-
pling, AC or DC.
Supply Jumper:
Input Jumper (IN):
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 566
DIGITALLY CONTROLLED PROGRAMMABLE GAIN AMPLIFIER
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5.
Turn on the power supply and connect the signal
generator to the IN BNC, or turrets as shown in
Figure 4.
6.
Monitor the output (BNC or test point) with an os-
cilloscope to observe a 1kHz 1VP–P signal.
7.
Using Tables 2, 3 or 4 set the gain as desired and
set the input to within the nominal linear input
range. Example: For a dual 5V supply operation
and a gain equal to five, the input to an LTC6910-1
should be set equal to or less than 2VP-P (see Table
2).
Table 2.
DC566A–A Gain Settings And Properties LTC6910-1
NOMINAL VOLTAGE GAIN NOMINAL LINEAR INPUT RANGE (VP–P)
G2 G1 G0 VOLTS/VOLT (dB) DUAL 5V
SUPPLY
SINGLE 5V
SUPPLY
SINGLE 3V
SUPPLY
NOMINAL INPUT IMPEDANCE
(KΩ)
1 0 0 0 -120 10 5 3 OPEN
0 0 1 -1 0 10 5 3 10
0 1 0 -2 6 5 2.5 1.5 5
0 1 1 -5 14 2 1 0.6 2
1 0 0 –10 20 1 0.5 0.3 1
1 0 1 -20 26 0.5 0.25 0.15 1
1 1 0 -50 34 0.2 0.1 0.06 1
1 1 1 -100 40 0.1 0.05 0.3 1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 566
DIGITALLY CONTROLLED PROGRAMMABLE GAIN AMPLIFIER
4
Table 3.
DC566A–B Gain Settings And Properties LTC6910-2
Table 4.
DC566A–C Gain Settings And Properties LTC6910-3
NOMINAL VOLTAGE GAIN NOMINAL LINEAR INPUT RANGE (VP–P)
G2 G1 G0 VOLTS/VOLT (dB) DUAL 5V
SUPPLY
SINGLE 5V
SUPPLY
SINGLE 3V
SUPPLY
NOMINAL INPUT IMPEDANCE
(K•)
1 0 0 0 -120 10 5 3 OPEN
0 0 1 -1 0 10 5 3 10
0 1 0 -2 6 5 2.5 1.5 5
0 1 1 -4 12 2.5 1.25 0.75 2.5
1 0 0 -8 18.06 125 0.625 0.375 1.25
1 0 1 -16 24.08 0.625 0.313 0.188 1.25
1 1 0 -32 30.1 0.313 0.156 0.094 1.25
1 1 1 -64 36.12 0.156 0.078 0.047 1.25
NOMINAL VOLTAGE GAIN NOMINAL LINEAR INPUT RANGE (VP–P)
G2 G1 G0 VOLTS/VOLT (dB) DUAL 5V
SUPPLY
SINGLE 5V
SUPPLY
SINGLE 3V
SUPPLY
NOMINAL INPUT IMPEDANCE
(K•)
1 0 0 0 -120 10 5 3 OPEN
0 0 1 -1 0 10 5 3 10
0 1 0 -2 6 5 2.5 1.5 5
0 1 1 -3 9.5 3.33 1.67 1 3.3
1 0 0 -4 12 2.5 1.25 0.75 2.5
1 0 1 -5 14 2 1 0.6 2
1 1 0 -6 15.6 1.67 0.83 0.5 1.7
1 1 1 -7 16.9 1.43 0.71 0.43 1.4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 566
DIGITALLY CONTROLLED PROGRAMMABLE GAIN AMPLIFIER
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