VRE104CA データシートの表示（PDF） - Thaler Corporation

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VRE104CA

Precision Reference Supplies

Thaler Corporation 

DISCUSSION OF PERFORMANCE

THEORY OF OPERATION

The following discussion refers to the schematic

below. A FET current source is used to bias a 6.3

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

4.5000V output. The gain is determined by the

resistor networks R3 and R4: G=1 + R4/R3. The 6.3

zener diode is used because it is the most stable

diode over time and temperature.

The current source provides a closely regulated

zener current, which 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 is nonlinear, this method

leaves a residual error over wide temperature

ranges.

To remove this residual error, Thaler has

developed a nonlinear compensation network of

thermistors and resistors that is used in the VRE104

series 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.

VRE104

APPLICATION INFORMATION

Figure 2 shows the proper connection of the

VRE104 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 VRE104 series voltage references have the

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 does not effect performance.

FIGURE 1

VRE104DS REV. C SEPT 1994

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