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PDF MC1494 Data sheet ( Hoja de datos )
| Número de pieza | MC1494 | |
| Descripción | LINEAR FOUR-QUADRANT MULTIPLIER INTEGRATED CIRCUIT | |
| Fabricantes | ON Semiconductor | |
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Order this document by MC1494/D
Linear Four-Quadrant
Multiplier
The MC1494 is designed for use where the output voltage is a linear
product of two input voltages. Typical applications include: multiply, divide,
square root, mean square, phase detector, frequency doubler, balanced
modulator/ demodulator, electronic gain control.
The MC1494 is a variable transconductance multiplier with internal
level–shift circuitry and voltage regulator. Scale factor, input offsets and output
offset are completely adjustable with the use of four external potentiometers.
Two complementary regulated voltages are provided to simplify offset
adjustment and improve power supply rejection.
• Operates with ±15 V Supplies
• Excellent Linearity: Maximum Error (X or Y) ±1.0 %
• Wide Input Voltage Range: ±10 V
• Adjustable Scale Factor, K (0.1 nominal)
• Single–Ended Output Referenced to Ground
• Simplified Offset Adjust Circuitry
• Frequency Response (3.0 dB Small–Signal): 1.0 MHz
• Power Supply Sensitivity: 30 mV/V typical
MC1494
LINEAR FOUR–QUADRANT
MULTIPLIER INTEGRATED
CIRCUIT
SEMICONDUCTOR
TECHNICAL DATA
16
1
P SUFFIX
PLASTIC PACKAGE
CASE 648C
ORDERING INFORMATION
Device
Tested Operating
Temperature Range Package
MC1494P
TA = 0° to + 70°C Plastic DIP
Figure 1. Multiplier Transfer Characteristic
10
8.0 X
6.0 Y
+
KXY
4.0
2.0
k=
1
10
0
– 2.0
– 4.0
– 6.0
– 8.0
–10
–10 – 8.0 – 6.0 – 4.0 – 2.0 0 2.0 4.0 6.0 8.0 10
VX, INPUT VOLTAGE (V)
MOTOROLA ANALOG IC DEVICE DATA
Figure 2. Linearity Error versus Temperature
1.00
0.75
0.50
0.25
0
– 50 – 25
0 25 50 75 100
TA, AMBIENT TEMPERATURE (°C)
125
© Motorola, Inc. 1996
Rev 0
1
1 page  
MC1494
Figure 15. Large Signal Voltage versus Frequency
1
20
2
10 1 With MC1456 Buffer Op Amp
2 No Op Amp, RL = 47 kΩ
0
100 1.0 k 10 k 100 k
f, FREQUENCY (Hz)
Figure 16. Scale Factor (K) versus Temperature
0.108
0.106
0.104
K Factor Adjusted for 1/10 at 25°C)
0.102
0.1
0.098
0.096
0.094
– 55 – 35 –15 5.0 25 45 65 85 105 125 145
TA, AMBIENT TEMPERATURE (°C)
CIRCUIT DESCRIPTION
Introduction
The MC1494 is a monolithic, four–quadrant multiplier that
operates on the principle of variable transconductance. It
features a single–ended current output referenced to ground
and provides two complementary regulated voltages for use
with the offset adjust circuits to virtually eliminate sensitivity
of the offset voltage nulls to changes in supply voltages.
As shown in Figure 17, the MC1494 consists of a multiplier
proper and associated peripheral circuitry to provide these
features.
Regulator
The regulator biases the entire MC1494 circuit making it
essentially independent of supply variation. It also provides
two convenient regulated supply voltages which can be used
in the offset adjust circuitry. The regulated output voltage at
Pin 2 is approximately + 4.3 V, while the regulated voltage at
Pin 4 is approximately – 4.3 V. For optimum temperature
stability of these regulated voltages, it is recommended that
|I2| = |I4| = 1.0 mA (equivalent load of 8.6 kΩ). As will be
shown later, there will normally be two 20 kΩ potentiometers
and one 50 kΩ potentiometer connected between Pins 2
and 4.
The regulator also establishes a constant current reference
that controls all of the constant current sources in the MC1494.
Note that all current sources are related to current I1 which is
determined by R1. For best temperatures performance, R1
should be 16 kΩ so that I1 ≈ 0.5 mA for all applications.
Multiplier
The multiplier section of the MC1494 (center section of
Figure 17) is nearly identical to the MC1495 and is discussed
in detail in Application Note AN489, Analysis and Basic
Operation of the MC1495. The result of this analysis is that
the differential output current of the multiplier is given by:
[IA – IB = ∆I
2VX VY
RXRYI1
Differential Current Converter
This portion of the circuitry converts the differential output
current (IA –IB) of the multiplier to a single–ended output
current (IO); IO = IA – IB
or
IO =
2VX VY
RXRYI1
The output current can be easily converted to an output
voltage by placing a load resistor RL from the output (Pin 14)
to ground (Figure 19) or by using an op amp as a
current–to–voltage converter (Figure 18). The result in both
circuits is that the output voltage is given by:
VO
=
2RL VX VY=
RXRYI1
KVXVY
where, K (scale factor) = 2RL
RXRYI1
DC OPERATION
Selection of External Components
For low frequency operation the circuit of Figure 18 is
recommended. For this circuit, RX = 30 kΩ, RY = 62 kΩ,
R1 = 16 kΩ and, hence, I1 ≈ 0.5 mA. Therefore, to set the
scale factor (K) equal to 1/10, the value of RL can be
calculated to be:
1
K=
= 2RL
10 RXRYI1
or RL = RXRYI1= (30 k) (62 k) (0.5 mA)
(2) (10)
20
RL = 46.5 k
Thus, a reasonable accuracy in scale factor can be
achieved by making RL a fixed 47 kΩ resistor. However, if it is
desired that the scale factor be exact, RL can be comprised of
a fixed resistor and a potentiometer as shown in Figure 18.
Therefore, the output is proportional to the product of the two
input voltages.
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page 
MC1494
Figure 23. Practical Divide Circuit
10 pF
510
30 k 62 k
11
9
+
12 7
MC1494
8
14
1
3
RL
50 k 22 k
10 pF
2
–
MC1741CP1 6
16 k 3
+
4
VZ
1N5240A
(10 V)
or
VO Equivalent
10
VX +
6
10 pF
5 15 13 4 P1 20 k 2
510
P3 50 k
7
VO
=
–10 VZ
VX
–15 V +15 V
P2 20 k
+15 V –15 V
0 < VX < +10 V
–10 V ≤ VZ ≤ +10 V
A simpler approach, since it does not involve breaking the
loop (thus making it more practical on a production basis), is:
1. Set VZ = 0 V and adjust the output offset potentiometer
(P3) until the output voltage (VO) remains at some (not
necessarily zero) constant value as VX is varied
between +1.0 V and +10 V.
2. Maintain VZ at 0 V, set VX at +10 V and adjust the
Y input offset potentiometer (P1) until VO = 0 V.
3. With VX = VZ, adjust the X input offset potentiometer
(P2) until the output voltage remains at some (not
necessarily –10 V) constant value as VZ = VX is varied
between +1.0 V and +10 V.
4. Maintain VX = VZ and adjust the scale factor
potentiometer (RL) until the average value of VO is
–10 V as VZ = VX is varied between +1.0 V and +10 V.
5. Repeat steps 1 through 4 as necessary to achieve
optimum performance.
Users of the divide circuit should be aware that the
accuracy to be expected decreases in direct proportion to the
denominator voltage. As a result, if VX is set to 10 V and
0.5% accuracy is available, then 5% accuracy can be
expected when VX is only 1.0 V.
In accordance with an earlier statement, VX may have only
one polarity (positive) while VZ may be either polarity.
Figure 24. Basic Square Root Circuit
KVO2
X
+
MC1494
+
–
+
VZ
–
+
KVO2 = –VZ
or
VO =
|VZ|
K
VZ ≤ 0 V
VO
Square Root
A special case of the divide circuit in which the two inputs
to the multiplier are connected together results in the square
root function as indicated in Figure 24. This circuit too may
suffer from latch–up problems similar to those of the divide
circuit. Note that only one polarity of input is allowed and
diode clamping (see Figure 25) protects against accidental
latch–up.
This circuit too, may be adjusted in the closed–loop mode:
1. Set VZ = –0.01 Vdc and adjust P3 (output offset) for
VO = 0.316 Vdc.
2. Set VZ to –0.9 Vdc and adjust P2 (“X” adjust) for
VO = +3.0 Vdc.
3. Set VZ to –10 Vdc and adjust P4 (gain adjust) for
VO = +10 Vdc.
4. Steps 1 through 3 may be repeated as necessary to
achieve desired accuracy.
NOTE: Operation near 0 V input may prove very inaccurate,
hence, it may not be possible to adjust VO to zero but rather
only to within 100 mV to 400 mV of zero.
AC APPLICATIONS
Wideband Amplifier with Linear AGC
If one input to the MC1494 is a DC voltage and a signal
voltage is applied to the other input, the amplitude of the
output signal can be controlled in a linear fashion by varying
the DC voltage. Hence, the multiplier can function as a DC
coupled, wideband amplifier with linear AGC control.
In addition to the advantage of linear AGC control, the
multiplier has three other distinct advantages over most other
types of AGC systems. First, the AGC dynamic range is
theoretically infinite. This stems from the basic fact that with
0 Vdc applied to the AGC, the output will be zero regardless
of the input. In practice, the dynamic range is limited by the
ability to adjust the input offset adjust potentiometers. By
using cermet multi–turn potentiometers, a dynamic range of
80 dB can be obtained. The second advantage of the
multiplier is that variation of the AGC voltage has no effect on
the signal handling capability of the signal port, nor does it
alter the input impedance of the signal port. This feature is
particularly important in AGC systems which are phase
sensitive. A third advantage of the multiplier is that the output
voltage swing capability and output impedance are
unchanged with variations in AGC voltage.
MOTOROLA ANALOG IC DEVICE DATA
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MC1494.PDF ] | |
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