OP293FS Analog Devices Inc, OP293FS Datasheet - Page 13

• Manufacturer Part Number: OP293FS
• Description: IC OPAMP GP 35KHZ DUAL 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of OP293FS

• Slew Rate: 0.015 V/µs
• Rohs Status: RoHS non-compliant
• Design Resources: 4 mA-to-20 mA Loop-Powered Temperature Monitor Using ADuC7060/1 (CN0145)
• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Gain Bandwidth Product: 35kHz
• Current - Input Bias: 20nA
• Voltage - Input Offset: 250µV
• Current - Supply: 30µA
• Current - Output / Channel: 25mA
• Voltage - Supply, Single/dual (±): 1.7 V ~ 36 V, ±0.85 V ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Op Amp Type: Precision
• No. Of Amplifiers: 2
• Bandwidth: 35kHz
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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:
Table I shows the values of R6 required for various temperature
ranges.
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:
but this can easily be changed by varying C1. The circuit oper-
ates well up to 500 Hz.
I
OUT
=



Temp Range
0°C to 70°C
–40°C to +85°C
–55°C to +150°C
∆
Table I. R6 Values vs. Temperature
T
f
OPERATING
OUT
∆
I
FS
=
V
CONTROL



(
T
AMBIENT
V
×
10
R6
10 kΩ
6.2 kΩ
3 kΩ
Hz
−
T
/
V
MIN
)
+
4 mA
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.:
V
CONTROL
1 IN/OUT
3 OUT/IN
4 IN/OUT
7
2 OUT/IN
5 CONT
6 CONT
200k
200k
100k
V
R2
R1
SS
R3
CD4066
R4
200k
1
2
S3
S4
2
3
S1
S2
75nF
C1
1/2 OP293
×
200k
A1
1.23 V
OP193/OP293/OP493
R8
256
5V
8
4
OUT/IN
IN/OUT 11
OUT/IN
IN/OUT
CONT 13
CONT 12
V
TRIANGLE
1
DD
5V
=
OUT
200k
14
3 mV
10
8
9
R6
5V
5V
5V
R5
200k
6
5
1/2 OP293
A2
R7
200k
7
SQUARE
OUT