OP293FS Analog Devices Inc, OP293FS Datasheet - Page 11

• 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

A Micropower False-Ground Generator
Some single-supply circuits work best when inputs are biased
above ground, typically at 1/2 of the supply voltage. In these
cases a false ground can be created by using a voltage divider
buffered by an amplifier. One such circuit is shown in Figure 6.
This circuit will generate a false-ground reference at 1/2 of the
supply voltage, while drawing only about 27 µA from a 5 V supply.
The circuit includes compensation to allow for a 1 µF bypass
capacitor at the false-ground output. The benefit of a large
capacitor is that not only does the false ground present a very low
dc resistance to the load, but its ac impedance is low as well. The
OP193 can both sink and source more than 5 mA, which improves
recovery time from transients in the load current.
A Battery-Powered Voltage Reference
The circuit of Figure 7 is a battery-powered voltage reference
that draws only 17 µA of supply current. At this level, two AA
alkaline cells can power this reference for more than 18 months.
At an output voltage of 1.23 V @ 25°C, drift of the reference is
only 5.5 µV/°C over the industrial temperature range. Load
regulation is 85 µV/mA with line regulation at 120 µV/V.
Design of the reference is based on the Brokaw bandgap core
technique. Scaling of resistors R1 and R2 produces unequal
currents in Q1 and Q2. The resulting ∆V
temperature-proportional voltage (PTAT) which, in turn, pro-
duces a larger temperature-proportional voltage across R4 and
R5, V1. The temperature coefficient of V1 cancels (first order)
the complementary to absolute temperature (CTAT) coefficient
of V
tempco is at a minimum. Bandgap references can have start-up
problems. With no current in R1 and R2, the OP193 is beyond
its positive input range limit and has an undefined output state.
Shorting Pin 5 (an offset adjust pin) to ground forces the output
high under these circumstances and ensures reliable startup
without significantly degrading the OP193’s offset drift.
BE1
240k
240k
. When adjusted to 1.23 V @ 25°C, output voltage
1 F
2
3
OP193
3
2
4
7
0.022 F
1
OP193
5V OR 12V
10k
V+
6
5
7
100k
4
100k
100
6
BE
V–
across R3 creates a
1 F
2.5V OR 6V
A Single-Supply Current Monitor
Current monitoring essentially consists of amplifying the voltage
drop across a resistor placed in series with the current to be
measured. The difficulty is that only small voltage drops can be
tolerated, and with low precision op amps this greatly limits the
overall resolution. The single-supply current monitor of Figure
8 has a resolution of 10 µA and is capable of monitoring 30 mA
of current. This range can be adjusted by changing the current
sense resistor R1. When measuring total system current, it may
be necessary to include the supply current of the current moni-
tor, which bypasses the current sense resistor, in the final result.
This current can be measured and calibrated (together with the
residual offset) by adjustment of the offset trim potentiometer,
R2. This produces a deliberate temperature dependent offset.
However, the supply current of the OP193 is also proportional
to temperature, and the two effects tend to track. Current in R4
and R5, which also bypasses R1, can be adjusted via a gain trim.
TO CIRCUIT
UNDER TEST
R5 20k
OUTPUT
ADJUST
C1
1000pF
240k
130k
V1
R1
R4
Q2
1
3
V
2
I
BE2
MAT-01AH
TEST
R1
1
R3 68k
100
V
BE
1.5M
R5
R2
OP193/OP293/OP493
7
5
3
2
100k
6
V
Q1
3
2
1
BE1
R3
OP193
100k
R2
OP193
V+
4
7
5
7
4
5
6
6
(2.5V TO 36V)
R2
9.9k
V
100mV/mA(I
OUT =
V
(1.23V @ 25°C)
V+
OUT
TEST
)