HA3-2556-9 查看數據表（PDF） - Intersil
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HA3-2556-9 Datasheet PDF : 15 Pages
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HA-2556
Square Root
The Square Root function can serve as a precision/wide
bandwidth compander for audio or video applications. A
compander improves the Signal to Noise Ratio for your
system by amplifying low level signals while attenuating or
compressing large signals (refer to Figure 17; X0.5 curve).
This provides for better low level signal immunity to noise
during transmission. On the receiving end the original signal
may be reconstructed with the standard Square function.
Communications
The Multiplier configuration has applications in AM Signal
Generation, Synchronous AM Detection and Phase
Detection to mention a few. These circuit configurations are
shown in Figures 6, 7 and 8. The HA-2556 is particularly
useful in applications that require high speed signals on all
inputs.
ACos(ωΑτ) VX+
HA-2556
VOUT
Audio
+
-
VX-
X
A
W
1/5V
+
∑
CCos(ωCτ) VY+
Carrier
+
-
Y
-
Z
VZ +
+
-
VY-
VZ -
W = A--1---0C---(Cos(ωC – ωA)τ + Cos(ωC + ωA)τ)
FIGURE 6. AM SIGNAL GENERATION
AM Signal VX+
HA-2556
VOUT
+
-
VX-
X
A
W
+
Carrier
1/5V
VY+
+
Y
-
∑
-
Z
VZ+
+
-
VY-
VZ-
LIKE THE FREQUENCY DOUBLER YOU GET AUDIO CENTERED AT DC
AND 2FC.
FIGURE 7. SYNCHRONOUS AM DETECTION
ACos(ωτ) VX+
HA-2556
VOUT
+
-
VX-
X
A
W
1/5V
ACos(ωτ+φ) VY+
+
Y
-
+
∑
-
Z
VZ +
+
-
VY-
VZ -
W = A-1---0-2- (Cos(φ) + Cos(2ωτ + φ))
DC COMPONENT IS PROPORTIONAL TO COS(f)
FIGURE 8. PHASE DETECTION
Each input X, Y and Z has similar wide bandwidth and input
characteristics. This is unlike earlier products where one
input was dedicated to a slow moving control function as is
required for Automatic Gain Control. The HA-2556 is
versatile enough for both.
Although the X and Y inputs have similar AC characteristics,
they are not the same. The designer should consider input
parameters such as small signal bandwidth, AC feedthrough
and 0.1dB gain flatness to get the most performance from
the HA-2556. The Y channel is the faster of the two inputs
with a small signal bandwidth of typically 57MHz versus
52MHz for the X channel. Therefore in AM Signal
Generation, the best performance will be obtained with the
Carrier applied to the Y channel and the modulation signal
(lower frequency) applied to the X channel.
Scale Factor Control
The HA-2556 is able to operate over a wide supply voltage
range ±5V to ±17.5V. The ±5V range is particularly useful in
video applications. At ±5V the input voltage range is reduced
to ±1.4V. The output cannot reach its full scale value with this
restricted input, so it may become necessary to modify the
scale factor. Adjusting the scale factor may also be useful
when the input signal itself is restricted to a small portion of
the full scale level. Here we can make use of the high gain
output amplifier by adding external gain resistors.
Generating the maximum output possible for a given input
signal will improve the Signal to Noise Ratio and Dynamic
Range of the system. For example, let’s assume that the
input signals are 1VPEAK each. Then the maximum output
for the HA-2556 will be 200mV. (1V x 1V)/(5V) = 200mV. It
would be nice to have the output at the same full scale as
our input, so let’s add a gain of 5 as shown in Figure 9.
A
VX+
+
-
VX-
HA-2556
X
VOUT
A
W
B
1/5V
VY+
+
Y
+
∑
-
Z
VZ +
+
1kΩ
RF
-
-
VY-
VZ -
ExternalGain = -R-----F-- + 1
RG
250Ω
RG
FIGURE 9. EXTERNAL GAIN OF 5
One caveat is that the output bandwidth will also drop by this
factor of 5. The multiplier equation then becomes:
W = 5----A-5----B-- = A × B
Current Output
Another useful circuit for low voltage applications allows the
user to convert the voltage output of the HA2556 to an output
current. The HA-2557 is a current output version offering
100MHz of bandwidth, but its scale factor is fixed and does not
have an output amplifier for additional scaling. Fortunately the
circuit in Figure 10 provides an output current that can be
6
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