AB-006 [ETC]
AB-006 - Make a -10V to +10V Adjustable Precision Voltage Source ; AB - 006 - 做一个-10V至+ 10V的可调式精密电压源
| 型号： | AB-006 |
| 厂家： | 
ETC |
| 描述： | AB-006 - Make a -10V to +10V Adjustable Precision Voltage Source
|
| 文件： | 总2页 (文件大小：24K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
AP P LICATION BULLETIN
Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Tel: (602) 746-1111 • Twx: 910-952-111 • Telex: 066-6491 • FAX (602) 889-1510 • Immediate Product Info: (800) 548-6132
Make a –10V to +10V Adjustable Precision Voltage Source
By R. Mark Stitt, (602) 746-7445
Many situations require a precision voltage source which
can be adjusted through zero to both positive and negative
output voltages. An example is a bipolar power supply.
Have you ever adjusted your unipolar lab supply down to
0V, then swapped the output leads and adjusted it back up to
get a negative voltage output? What happened to your circuit
when the input from the low impedance source went open
circuit? Were you able to actually adjust the output to 0V, or
did a small voltage offset limit the range? This precision
bipolar voltage source can solve these problems.
However, a simpler solution is to use a single voltage
reference and a precision unity-gain inverting amplifier. If
you use a precision difference amplifier for the unity-gain
inverting amplifier, the circuit requires just two chips and a
potentiometer.
To understand how the circuit works, first consider the –
1.0V/V to +1.0V/V linear gain control amplifier shown in
Figure 1. An INA105 difference amplifier is used in a unity-
gain inverting amplifier configuration. A potentiometer is
connected between the input and ground. The slider of the
pot is connected to the noninverting input of the unity-gain
inverting amplifier. (The noninverting input of a unity-gain
inverting amplifier would normally be connected to ground.)
With the slider at the bottom of the pot, the circuit is a
normal precision unity-gain inverting amplifier with a gain
of –1.0V/V ±0.01% max. With the slider at the top of the
pot, the circuit is a normal precision voltage follower with a
gain of +1.0V/V ±0.001% max. With the slider in the center,
there is equal positive and negative gain for a net gain of 0V/
V. The accuracy between –1.0V/V and +1.0V/V will nor-
mally be limited by the accuracy of the pot. Precision 10-
turn pots are available with 0.01% linearity.
Perhaps the most obvious implementation of a bipolar volt-
age source would be to use a bipolar voltage reference.
INA105
Difference Amp
2
5
6
VIN
R1
25kΩ
R2
25kΩ
R3
25kΩ
VOUT
=
10kΩ
Linear
3
1
+VIN to –VIN
The –1.0V/V to +1.0V/V linear gain control amplifier has
many applications. With the addition of a precision +10.0V
reference as shown in Figure 2, it becomes a –10V to +10V
adjustable precision voltage source.
R4
25kΩ
VOUT = +VIN, Slider at Top of Pot.
VOUT = 0V, Slider at Center of Pot.
VOUT = –VIN, Slider at Bottom of Pot.
FIGURE 1. –1.0V/V to +1.0V/V Linear Gain Control Am-
plifier.
+VS
2
V+
INA105
Difference Amp
5
REF102
2
6
10V
Out
R1
R2
25kΩ
25kΩ
Gnd
4
R3
25kΩ
6
VOUT
+10V to –10V
=
10kΩ
Linear
3
1
VOUT = +10V, Slider at Top of Pot.
VOUT = 0V, Slider at Center of Pot.
VOUT = –10V, Slider at Bottom of Pot.
R4
25kΩ
FIGURE 2. –10V to +10V Adjustable Precision Voltage Source.
1990 Burr-Brown Corporation
AB-006
Printed in U.S.A. April, 1990
In many instances adjustable voltage sources need the ability
to drive high-capacitance loads such as power-supply bypass
capacitors. The additional circuitry needed to drive high
capacitance is shown in Figure 3. For stability, keep CLOAD•R3
< 0.5•R2•C2. Since access to the op amp inverting input is
needed, the unity-gain inverting amplifier is made with an
op amp and discrete resistors. For precision, R1 and R2 must
be accurately matched. Also, load current flows in R3. The
resulting voltage drop adds to the required swing at the
output of the op amp. Keep the voltage drop across R3 low
—less than 1V at full load—to prevent the amplifier output
from swinging too close to its power-supply rail.
For applications with substantial volume (e.g. 5k ea/year) a
version of the INA105 with the op amp inverting input
brought out is available as a special (2A660). Inquire with
marketing about price and delivery.
+VS
2
V+
R1
10kΩ
R2
10kΩ
REF102
10V
Out
6
+10V
C2
Gnd
4
0.01µF
R3
50Ω
VOUT
+10V to –10V
=
OPA27
10kΩ
Linear
VOUT = +10V, Slider at Top of Pot.
VOUT = 0V, Slider at Center of Pot.
VOUT = –10V, Slider at Bottom of Pot.
CLOAD
FIGURE 3. –10V to +10V Adjustable Precision Voltage Source with High Capacitance-Load Drive Capability.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
2
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