AD606JN Analog Devices Inc, AD606JN Datasheet - Page 8

• Manufacturer Part Number: AD606JN
• Description: Amplifier IC
• Manufacturer: Analog Devices Inc

Specifications of AD606JN

• No. Of Amplifiers: 1
• Bandwidth: 50MHz
• No. Of Pins: 16
• Mounting Type: Through Hole
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• Package / Case: 16-DIP
• Rohs Status: RoHS non-compliant
• Amplifier Type: Logarithmic
• Number Of Circuits: 1
• Output Type: Differential
• Current - Input Bias: 4µA
• Current - Supply: 13mA
• Current - Output / Channel: 1.2mA
• Voltage - Supply, Single/dual (±): 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• -3db Bandwidth: -
• Slew Rate: -
• Gain Bandwidth Product: -
• Voltage - Input Offset: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD606
Adjustment Procedure
The slope and intercept adjustments interact; this can be mini-
mized by reducing the resistance of R1 and R2, chosen here to
minimize power drain. Calibration can be achieved in several
ways: The simplest is to apply an RF input at the desired oper-
ating frequency which is amplitude modulated at a relatively
low frequency (say 1 kHz to 10 kHz) to a known modulation
index. Thus, one might choose a ratio of 2 between the maxi-
mum and minimum levels of the RF amplitude, corresponding
to a 6 dB (strictly, 6.02 dB) change in input level. The average
RF level should be set to about –35 dBm (the midpoint of the
AD606’s range). R2 is then adjusted so that the 6 dB input
change results in the desired output voltage change, for ex-
ample, 226 mV at 37.5 mV/dB.
A better choice would be a 4:1 ratio (12.04 dB), to spread the
residual error out over a larger segment of the whole transfer
function. If a pulsed RF generator is available, the decibel incre-
ment might be enlarged to 20 dB or more. Using just a fixed-
level RF generator, the procedure is more time consuming, but
is carried out in just the same way: manually change the level by
a known number of decibels and adjust R2 until V
the corresponding voltage.
Having adjusted the slope, the intercept may now be simply ad-
justed using a known input level. A value of –35 dBm (397.6 mV
rms, or 400 mV to within 0.05 dB) is recommended, and if the
standard scaling is used (P
then V
A Low Cost Audio Through RF Power Meter
Figure 7 shows a simple power meter that uses the AD606 and
an ICL7136 3-1/2 digit DMM IC driving an LCD readout. The
circuit operates from a single +5 V supply and provides direct
readout in dBm, with a resolution of 0.1 dBm.
INPUT
INPUT
dBm
dBV
LOG
*
FOR AUDIO MEASUREMENTS CHANGE
C1, C2, AND C3 TO 4.7 F; POSITIVE POLARITY
CONNECT TO PINS 1, 16
should be set to +2 V at this input level.
51.1
NC = NO CONNECT
174
100pF
100pF
C2*
C1*
X
= –88.33 dBm, V
0.1 F
NC
AD606JN
+5V
NC
NC
150pF
C3*
Figure 7. A Low Cost RF Power Meter
Y
= 37.5 mV/dB),
LOG
varies by
1M
FREQUENCY
R1
OPTIONAL
COUNTER
DRIVE TO
200
+5V
–8–
54.9k
54.9k
100k
100k
In contrast to the limited dynamic range of the diode and
thermistor-styled sensors used in power meters, the AD606 can
measure signals from below –80 dBm to over +10 dBm. An
optional 50
form the lower arm of an external attenuator to accommodate
larger signal levels. By the simple expedient of using a 13 dB
attenuator, the LCD reading now becomes dBV (decibels above
1 V rms). This requires a series resistor of 174 , presenting an
input resistance of 224 . Alternatively, the input resistance can
be raised to 600
note that the AD606 inputs must be ac coupled. To extend the
low frequency range, use larger coupling capacitors and an
external loop filter, as outlined earlier.
The nominal 0.5 V to 3.5 V output of the AD606 (for a –75 dBm
to +5 dBm input) must be scaled and level shifted to fit within
the +1 V to +4.5 V common-mode range of the ICL7136 for
the +5 V supply used. This is achieved by the passive resistor
network of R1, R2, and R3 in conjunction with the bias net-
works of R4 through R7, which provide the ICL7136 with its
reference voltage, and R9 through R11, which set the intercept.
The ICL7136 measures the differential voltage between INHI
and INLO, which ranges from –75 mV to +5 mV for a
–75 dBm to +5 dBm input.
To calibrate the power meter, first adjust R6 for 100 mV be-
tween REF HI and REF LO. This sets the initial slope. Then
adjust R10 to set INLO 80 mV higher than INHI. This sets the
initial intercept. The slope and intercept may now be adjusted
using a calibrated signal generator as outlined in the previous
section.
To extend the low frequency limit of the system to audio fre-
quencies, simply change C1, C2, and C3 to 4.7 F.
The limiter output of the AD606 may be used to drive the high-
impedance input of a frequency counter.
5k
R10
R8
R9
R2
R3
+5V
+5V
SIGNAL
INPUT
0dBm
FOR
80mV
2.433V NOM
2.513V NOM
4.99k
4.32k
500
162
termination is included in the figure; this could
R4
R5
R6
R7
+5V
1 F
using 464
C4
100mV
36
35
32
31
REF HI
REF LO
COMM
INLO
INHI
ICL7136CPL
and 133 . It is important to
+5V
V–
0.1 F
40
39
38
34
33
0.047 F
180k
1.8M
0.1 F
50pF
0.1 F
DISPLAY
–75.0
REV. B