OP295GBC View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
OP295GBC Datasheet PDF : 12 Pages
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OP295/OP495
Table I. Single Supply Low Noise Preamp Performance
R1
R3, R4
en @ 100 Hz
en @ 10 Hz
ISY
IB
Bandwidth
Closed-Loop Gain
IC = 1.85 mA
270 Ω
200 Ω
3.15 nV/√Hz
4.2 nV/√Hz
4.0 mA
11 µA
1 kHz
1000
IC = 0.5 mA
1.0 kΩ
910 Ω
8.6 nV/√Hz
10.2 nV/√Hz
1.3 mA
3 µA
1 kHz
1000
Driving Heavy Loads
The OP295/OP495 is well suited to drive loads by using a
power transistor, Darlington or FET to increase the current to
the load. The ability to swing to either rail can assure that the
device is turned on hard. This results in more power to the load
and an increase in efficiency over using standard op amps with
their limited output swing. Driving power FETs is also possible
with the OP295/OP495 because of its ability to drive capacitive
loads of several hundred picofarads without oscillating.
Without the addition of external transistors the OP295/OP495
can drive loads in excess of ± 15 mA with ± 15 or +30 volt
supplies. This drive capability is somewhat decreased at lower
supply voltages. At ± 5 volt supplies the drive current is ± 11 mA.
Driving motors or actuators in two directions in a single supply
application is often accomplished using an “H” bridge. The
principle is demonstrated in Figure 3a. From a single +5 volt
supply this driver is capable of driving loads from 0.8 V to 4.2 V
in both directions. Figure 3b shows the voltages at the inverting
and noninverting outputs of the driver. There is a small crossover
glitch that is frequency dependent and would not cause problems
0 ≤ VIN ≤ 2.5V 5k
2N2222
10k
+5V
OUT PU TS
2N2222
1.67V
10k 10k 2N2907
2N2907
Figure 3a. “H” Bridge
100
90
10
0%
2V
2V
1ms
Figure 3b. “H” Bridge Outputs
unless this was a low distortion application such as audio. If this
is used to drive inductive loads, be sure to add diode clamps to
protect the bridge from inductive kickback.
Direct Access Arrangement
OP295/OP495 can be used in a single supply Direct Access Ar-
rangement (DAA) as is shown an in Figure 4. This figure shows
a portion of a typical DM capable of operating from a single
+5 volt supply and it may also work on +3 volt supplies with
minor modifications. Amplifiers A2 and A3 are configured so
that the transmit signal TXA is inverted by A2 and is not in-
verted by A3. This arrangement drives the transformer differen-
tially so that the drive to the transformer is effectively doubled
over a single amplifier arrangement. This application takes ad-
vantage of the OP295/OP495’s ability to drive capacitive loads,
and to save power in single supply applications.
390pF
0.1µF
RXA
37.4kΩ
A1
0.0047µF
3.3kΩ
20kΩ
OP295/
OP495
20kΩ
OP295/
OP495
A2
475Ω
0.1µF 20kΩ
TXA
22.1kΩ
750pF
20kΩ
20kΩ
0.033µF
1:1
2.5V REF
OP295/
OP495
A3
Figure 4. Direct Access Arrangement
A Single Supply Instrumentation Amplifier
The OP295/OP495 can be configured as a single supply instru-
mentation amplifier as in Figure 5. For our example, VREF is set
V+
equal to 2 and VO is measured with respect to VREF. The in-
put common-mode voltage range includes ground and the out-
put swings to both rails.
VIN
R1
100k
VREF
V+ 1/2
OP295/
1/2
5 8 OP495
OP295/
7
VO
3
OP495
6
4
1
2
R2
R3
R4
20k
20k
RG
100k
( ) VO =
5 + 200k
RG
VIN + VREF
Figure 5. Single Supply Instrumentation Amplifier
Resistor RG sets the gain of the instrumentation amplifier. Mini-
mum gain is 6 (with no RG). All resistors should be matched in
absolute value as well as temperature coefficient to maximize
–8–
REV. B
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