AD600JR Analog Devices Inc, AD600JR Datasheet - Page 20

• Manufacturer Part Number: AD600JR
• Description: IC AMP VGA DUAL LN 50MA 16SOIC
• Manufacturer: Analog Devices Inc
• Series: X-AMP®r

Specifications of AD600JR

• Rohs Status: RoHS non-compliant
• Amplifier Type: Variable Gain
• Number Of Circuits: 2
• Slew Rate: 275 V/µs
• -3db Bandwidth: 35MHz
• Current - Input Bias: 350nA
• Current - Supply: 11mA
• Current - Output / Channel: 50mA
• Voltage - Supply, Single/dual (±): ±4.75 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Output Type: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -

AD600/AD602
The output of A2 is ac-coupled via another 12 Hz high-pass
filter formed by C2 and the 6.7 kΩ input resistance of the
AD636. The averaging time constant for the rms-dc converter
is determined by C4. The unbuffered output of the AD636 (at
Pin 8) is compared with a fixed voltage of 316 mV set by the
positive supply voltage of 6 V and Resistors R6 and R7. V
proportional to this voltage, and systems requiring greater
calibration accuracy should replace the supply dependent
reference with a more stable source.
Any difference in these voltages is integrated by the op amp
U3B, with a time constant of 3 ms formed by the parallel sum
of R6/R7 and C3. Now, if the output of the AD600 is too high,
V rms is greater than the setpoint of 316 mV, causing the output
of U3B—that is, V
noninverting). A fraction of V
gain-control inputs of the AD600, so causing the gain to be
reduced, as required, until V rms is exactly equal to 316 mV, at
which time the ac voltage at the output of A2 is forced to be
exactly 316 mV rms. This fraction is set by R4 and R5 such that
a 15.625 mV change in the control voltages of A1 and A2—
which would change the gain of the cascaded amplifiers by
1 dB—requires a change of 100 mV at V
since A2 is forced to operate at an output level well below its
capacity, waveforms of high crest factor can be tolerated
throughout the amplifier.
(SINE WAVE)
1V rms
INPUT
MAX
115Ω
U3A
R1
15.625mV/dB
AD712
OUT
1/2
R2 200Ω
—to ramp up (note that the integrator is
133kΩ
V
CAL
0dB
G
R3
Figure 41. The Output of This Three-IC Circuit Is Proportional to the Decibel Value of the rms Input
R4
3.01kΩ
OUT
C1LO
A1LO
A2LO
C2LO
GAT1
GAT2
A1HI
A2HI
is connected to the inverting
1
2
3
4
5
6
7
8
OUT
+
–
–
+
16.2kΩ
R5
. Notice here that
AD600
0.1µF
U1
C1
A1
A2
REF
16
15
14
13
12
11
10
9
REF
VPOS
A2CM
C1HI
A1CM
A1OP
VNEG
A2OP
C2HI
is
Rev. E | Page 20 of 28
+6V
DEC
–6V
DEC
C2
2µF
To check the operation, assume an input of 10 mV rms is
applied to the input, which results in a voltage of 3.16 mV rms
at the input to A1, due to the 10 dB loss in the attenuator. If the
system operates as claimed, V
This being the case, the gain of both A1 and A2 is 20 dB and the
output of the AD600 is therefore 100 times (40 dB) greater than
its input, which evaluates to 316 mV rms, the input required at
the
AGC circuits that need strong temperature compensation for
the internal kT/q scaling, these voltages, and thus the output of
this measurement system, are temperature stable, arising
directly from the fundamental and exact exponential
attenuation of the ladder networks in the AD600.
Typical results are presented for a sine wave input at 100 kHz.
Figure 42 shows that the output is held close to the setpoint of
316 mV rms over an input range in excess of 80 dB.
DEC
–6V
V
rms
AD636
NC
NC
NC
AF/RF
OUTPUT
Figure 42. RMS Output of A2 Held Close to the Setpoint 316 mV
450
425
400
375
350
325
300
275
250
225
200
175
150
NC = NO CONNECT
1
2
3
4
5
6
7
10µ
VINP
VNEG
CAVG
VLOG
BFOP
BFIN
to balance the loop. Finally, note that unlike most
AD636
4.7µF
C4
U2
100µ
COMM
VPOS
LDLO
V
for an Input Range of over 80 dB
RMS
14
13
12
11
10
9
8
AD712
1/2
1m
INPUT SIGNAL (V rms)
NC
NC
NC
3.16kΩ
U3B
R6
OUT
10m
0V = 0dB (AT 10mV rms)
(and hence V
+100mV/dB
R7
56.2kΩ
C3
1µF
+316.2mV
+6V DEC
100m
DEC
DEC
V OUT
+6V
–6V
POWER SUPPLY
DECOUPLING
G
FB
FB
) should be 0.
NETWORK
1
–6V
+6V
0.1µF
0.1µF
10