MC1494 데이터 시트보기 (PDF) - ON Semiconductor
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MC1494 Datasheet PDF : 16 Pages
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MC1494
demodulation, then a 1% phase vector error will represent a
1% amplitude error a the phase angle of interest.
X = Aë 0°
Y = Bë 0°
ABë φ
V
φ
ABë0°
Figure 20. Phase Vector Error
Circuit Layout
If wideband operation is desired, careful circuit layout
must be observed. Stray capacitance across RX and RY
should be avoided to minimize peaking (caused by a zero
created by the parallel RC circuit).
DC APPLICATIONS
Squaring Circuit
If the two inputs are connected together, the resultant
function is squaring:
VO = KV2
where K is the scale factor (see Figure 21).
However, a more careful look at the multiplier’s defining
equation will provide some useful information. The output
voltage, without initial offset adjustments is given by:
VO = K(VX + Viox –VX off) (VY + Vioy –VY off) + VOO
(Refer to “Definitions” section for an explanation of terms.)
With VX = VY = V (squaring) and defining;
∈x = Viox – Vx (off)
∈y = Vioy – Vy (off)
The output voltage equation becomes:
VO = KVx2+ KVx (∈x + ∈y) + K∈x ∈y + VOO
V
10 pF
510
11
9
+
10
+
30 k
12
62 k
7
+15 V -15 V
8
15
MC1494
5
+
14
136
16 k
13 4 51 k 2
20 k
P1
20 k
Output
Offset
Input
Offset
P3
P4
50 k
22 k
10 pF
2
-
6
MC1456
3
+
7
4
-15 V +15 V
Figure 21. MC1494 Squaring Circuit
-V2
VO = 10
This shows that all error terms can be eliminated with only
three adjustment potentiometers, eliminating one of the
input offset adjustments. For instance, if the “X” input offset
adjustment is eliminated, ∈x is determined by the internal
offset (Viox) but ∈y is adjustable to the extent that the
(∈x+∈y) term can be zeroed. Then the output offset
adjustment is used to adjust the Voo term and thus zero the
remaining error terms. An AC procedure for nulling with
three adjustments is:
A. AC Procedure:
1. Connect oscillator (1.0 kHz, 15 Vpp) to input.
2. Monitor output at 2.0 kHz with tuned voltmeter and
adjust P4 for desired gain ( Be sure to peak
response of voltmeter).
3. Tune voltmeter to 1.0 kHz and adjust P1 for a
minimum output voltage.
4. Ground input and adjust P3 (output offset) for
0 Vdc out.
5. Repeat steps 1 through 4 as necessary.
B. DC Procedure:
1. Set VX = VY = 0 V and adjust P3 (output offset
potentiometer) such that VO = 0 Vdc.
2. Set VX = VY = 1.0 V and adjust P1 (Y input offset
potentiometer) such that the output voltage is
– 0.100 V.
3. Set VX = VY = 10 Vdc and adjust P4 (load resistor)
such that the output voltage is –10 V.
4. Set VX = VY = –10 Vdc and check that VO = –10 V.
5. Repeat steps 1 through 4 as necessary.
Divide
Divide circuits warrant a special discussion as a result of
their special problems. Classic feedback theory teaches that
if a multiplier is used as a feedback element in an operational
amplifier circuit, the divide function results. Figure 22
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