VRE105 ETC1 [List of Unclassifed Manufacturers], VRE105 Datasheet - Page 4

• Manufacturer Part Number: VRE105
• Description: Precision Reference Supplies
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

4-35
VRE105
THEORY OF OPERATION
below. A FET current source is used to bias a 6.3V
zener diode. The zener voltage is divided by the
resistor network R1 and R2. This voltage is then
applied to the noninverting input of the operational
amplifier which amplifies the voltage to produce a
5.000V output. The gain is determined by the
resistor networks R3 and R4: G=1 + R4/R3. The
6.3V zener diode is used because it is the most
stable diode over time and temperature.
zener current, which determines the slope of the
reference's voltage vs. temperature function. By
trimming the zener current, a lower drift over
temperature can be achieved. But since the voltage
vs. temperature function is nonlinear, this method
leaves a residual error over wide temperature
ranges.
has developed a nonlinear compensation network of
thermistors and resistors that is used in the VRE105
series
eliminates most of the nonlinearity in the voltage vs.
temperature function. By then adjusting the slope,
Thaler Corporation produces a very stable voltage
over wide temperature ranges. This network is less
than 2% of the overall network resistance so it has
a negligible effect on long term stability.
VRE107
The following discussion refers to the schematic
The current source provides a closely regulated
To remove this residual error, Thaler Corporation
references.
This
DISCUSSION OF PERFORMANCE
proprietary
network
APPLICATION INFORMATION
VRE105 series voltage reference with the optional
trim resistors. When trimming the VRE107, the
positive voltage should be trimmed first since the
negative voltage tracks the positive side. Pay careful
attention to the circuit layout to avoid noise pickup
and voltage drops in the lines.
ground terminal brought out on two pins (pin 6 and
pin 7) which are connected together internally. This
allows the user to achieve greater accuracy when
using a socket. Voltage references have a voltage
drop across their power supply ground pin due to
quiescent current flowing through the contact
resistance. If the contact resistance was constant
with time and temperature, this voltage drop could be
trimmed out. When the reference is plugged into a
socket, this source of error can be as high as 20ppm.
By connecting pin 7 to the power supply ground and
pin 6 to a high impedance ground point in the
measurement circuit, the error due to the contact
resistance can be eliminated. If the unit is soldered
into place the contact resistance is sufficiently small
that it doesn't effect performance.
Figure 1 shows the proper connection of the
The VRE105 series voltage references have the
VRE105DS REV. C SEPT 1994