OP193 查看數據表（PDF） - Analog Devices
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OP193 Datasheet PDF : 16 Pages
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OP193/OP293/OP493
From the formulas, it can be seen that if the span trim is
adjusted before the zero trim, the two trims are not interactive,
which greatly simplifies the calibration procedure.
Calibration of the transmitter is simple. First, the slope of the
output current versus temperature is calibrated by adjusting the
span trim, R7. A couple of iterations may be required to be sure
the slope is correct.
Once the span trim has been completed, the zero trim can be made.
Remember that adjusting the zero trim will not affect the gain.
The zero trim can be set at any known temperature by adjusting
R5 until the output current equals:
( ) I
OUT
=
∆I FS
∆TOPERATING
TAMBIENT
− TMIN
+ 4 mA
Table I shows the values of R6 required for various temperature
ranges.
Table I. R6 Values vs. Temperature
Temp Range
0°C to 70°C
–40°C to +85°C
–55°C to +150°C
R6
10 kΩ
6.2 kΩ
3 kΩ
A Micropower Voltage Controlled Oscillator
An OP293 in combination with an inexpensive quad CMOS
analog switch forms the precision VCO of Figure 12. This cir-
cuit provides triangle and square wave outputs and draws only
50 µA from a single 5 V supply. A1 acts as an integrator; S1
switches the charging current symmetrically to yield positive and
negative ramps. The integrator is bounded by A2 which acts as
a Schmitt trigger with a precise hysteresis of 1.67 volts, set by
resistors R5, R6, and R7, and associated CMOS switches. The
resulting output of A1 is a triangle wave with upper and lower
levels of 3.33 and 1.67 volts. The output of A2 is a square wave
with almost rail-to-rail swing. With the components shown,
frequency of operation is given by the equation:
f =V
V × 10 Hz / V
OUT
CONTROL
but this can easily be changed by varying C1. The circuit oper-
ates well up to 500 Hz.
VCONTROL
R1
200k⍀
R2
200k⍀
R3
100k⍀
C1
75nF
5V
2
8
A1
1
1/2 OP293
3
4
5V
R5
200k⍀
6
A2
1/2 OP293
5
SQUARE
OUT
7
R4
200k⍀
R8
200k⍀
TRIANGLE
OUT
R6
200k⍀
5V
R7
200k⍀
1 IN/OUT
2 OUT/IN
CD4066
S1
VDD 14
5V
CONT 13
3 OUT/IN
S2
CONT 12
4 IN/OUT
IN/OUT 11
5 CONT
6 CONT
7 VSS
OUT/IN 10
S3
OUT/IN 9 5V
S4
IN/OUT 8
Figure 12. Micropower Voltage Controlled Oscillator
A Micropower, Single-Supply Quad Voltage Output 8-Bit DAC
The circuit of Figure 13 uses the DAC8408 CMOS quad 8-bit
DAC and the OP493 to form a single-supply quad voltage out-
put DAC with a supply drain of only 140 µA. The DAC8408 is
used in the voltage switching mode and each DAC has an out-
put resistance (≈10 kΩ) independent of the digital input code.
The output amplifiers act as buffers to avoid loading the DACs.
The 100 kΩ resistors ensure that the OP493 outputs will swing
to within 1/2 LSB of ground, i.e.:
1 1.23 V
×
= 3 mV
2 256
REV. B
–13–
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