參數(shù)資料
型號: VRE210MA
英文描述: Voltage Reference
中文描述: 電壓基準
文件頁數(shù): 4/5頁
文件大小: 192K
代理商: VRE210MA
THEORY OF OPERATION
The following discussion refers to the schematic
below. In operation, approximately 6.3 volts is
applied to the noninverting input of the op amp. The
voltage is amplified by the op amp to produce a
10.000V output. The gain is determined by the
networks R1 and R2: G=1 + R2/R1. The 6.3V zener
diode is used because it is the most stable diode
over time and temperature.
The zener operating current is derived from the
regulated output voltage through R3. This feedback
arrangement provides a closely regulated zener
current. This current determines the slope of the
references' voltage vs. temperature function. By
trimming the zener current a lower drift over
temperature can be achieved. But since the voltage
vs.
temperature
function
compensation technique is not well suited for wide
temperature ranges.
is
nonlinear
this
Thaler Corporation has developed a nonlinear
compensation network of thermistors and resistors
that is used in the VRE series voltage references.
This proprietary network 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. By using highly stable
resistors in our network, we produce a voltage
reference that also has very good long term
stability.
DISCUSSION OF PERFORMANCE
VRE210
FIGURE 1
APPLICATION INFORMATION
Figure 2 shows the proper connection of the
VRE210 series voltage references with the optional
trim resistors. Pay careful attention to the circuit
layout to avoid noise pickup and voltage drops in the
lines.
The VRE210 series voltage references have the
ground terminal brought out on two pins (pin 9 and
pin 10) 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 10 to the power supply ground and
pin 9 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 does not effect performance.
VRE210DS REV. C JUNE 1995
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