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參數資料
| 型號： | MC1494 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | LINEAR FOUR-QUADRANT MULTIPLIER INTEGRATED CIRCUIT |
| 中文描述： | 線性四象限乘法器集成電路 |
| 文件頁數： | 5/16頁 |
| 文件大小： | 319K |
| 代理商： | MC1494 |
MC1494
5
MOTOROLA ANALOG IC DEVICE DATA
1
2
20
0
10
100
1.0 k
10 k
100 k
f, FREQUENCY (Hz)
Figure 15. Large Signal Voltage versus Frequency
Figure 16. Scale Factor (K) versus Temperature
0.108
0.106
0.104
0.102
0.1
0.098
0.096
0.094
– 55
– 35
–15
5.0
TA, AMBIENT TEMPERATURE (
°
C)
25
45
65
85
105
125
K
O
145
1
2
With MC1456 Buffer Op Amp
No Op Amp, RL = 47 k
K Factor Adjusted for 1/10 at 25
°
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 k
). As will be
shown later, there will normally be two 20 k
potentiometers
and one 50 k
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 k
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:
RXRYI1
2VX VY
IA – IB =
I
Therefore, the output is proportional to the product of the two
input voltages.
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
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= KVXVY
RXRYI1
IO =
or
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 k
, RY = 62 k
,
R1 = 16 k
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
10
RXRYI1
or RL =RXRYI1
(2) (10)
=
K =
2RL
=(30 k) (62 k) (0.5 mA)
20
RL = 46.5 k
Thus, a reasonable accuracy in scale factor can be
achieved by making RL a fixed 47 k
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.
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