NF Corporation:Document

Lock-in Amplifier/Preamplifier

Low Noise DC Voltage Source
LP6016-01/LP6016-01P

Applications

Improved Stability of Voltage Controlled Crystal Oscillator | Reference voltage source for A/D converter | Improvement of S/N Ratio of Photodiode Output

Improved Stability of Voltage Controlled Crystal Oscillator

Phase noise, frequency accuracy and frequency stability are normally measured during performance evaluation for crystal oscillators. For high performance voltage controlled devices such as VCXO, TCXO and OCXO, they are typically susceptible to noise and stability of their control voltage.

*VCXO (Voltage Controlled Crystal Oscillator), TCXO (Temperature Compensated Crystal Oscillator), OCXO (Oven Controlled Crystal Oscillator)

VCXO frequency measurement---different control voltage sources

A low noise and stable control voltage source is used to evaluate voltage control devices.
In the block diagram below, the output noise was measured with a general linear power supply or LP6016-01 as the control voltage source.

Measurement Conditions

- TCVCXO Center Frequency: approx. 30 MHz;
- Ｍeasurement Cycle: 1 Hz;
- Number of Measurements: 40,000 times;
- Total Measurement Time: approx. 11 hours;
- Ambient Temperature: 23 ±5°C.

The upper part of the graph is the time change of the output frequency. When the LP series is used, the output frequency is stable for a long time.

The bottom part of the graph is a histogram display of the output frequency. The deviation from the center frequency is way smaller with our LP Series.

As we can see, the LP series is able to supply a stable voltage for a long time. A stable control voltage source is required to evaluate not only crystal oscillators but also voltage control components.

Measurement Block Diagram

Dual-channel of positive voltage are used for control voltage and power supply.

Reference voltage source for A/D converter

The reference voltage of the A/D converter affects the conversion accuracy, and the voltage noise and fluctuations are related to output performance. A low noise and stable voltage source is required for performance testing of A/D converters.

Output voltage of A/D converter---Difference between control voltage sources

In the block diagram below, the output voltage was measured when two different voltage sources were used, while the A/D converter reference voltage is at 4.096V and the input voltage is at 2.5V (≈ full scale).

Measurement Conditions

The output voltage is applied 80 million times in 80 minutes, and the variation is displayed in a histogram.

When the LP series is used, the variation in the LSB of the AD converter was reduced.

Measurement Block Diagram

Dual-channel of positive voltage are used for control voltage and power supply.

Improvement of S/N Ratio of Photodiode Output

When using a highly sensitive sensor, the noise of from its power source would affect the sensor's sensitivity. With different bias power sources applied to the photodiode, the output S/N ratios are compared below.

Video : SNR Improvement of Photodiode by Low Noise DC Voltage Source

Photodiodes are widely used as light receiving elements for lasers, and in order to increase its sensitivity, a reverse bias voltage (Vb) is applied. A low-noise bias voltage source is required for sensitive photodetection.

Detection Signal Comparison---Difference Between Drive Power Supply and Bias Voltage Source

The detection signals were compared between the drive power supply (constant current control) and the bias voltage source using LP6016-01 or a general linear power supply.