TZA500

PRINCIPLES OF OPERATION The TZA500 measures small currents e.g. optical power via a photodiode. Photodiodes are useful for power measurement in the visible and near infra-red due to their inherent sensitivity and speed of measurement. Photodiodes produce a current which is proportional to the inci ...Read more

The transimpedance amplifier TZA500 is designed
for precise measurement of current, from pA to mA.
The output is a voltage linearly proportional to the
input current.

The TZA500 is very flexible with USB and hard-wire
interface control of gain, bandwidth and polarity.
A graphical user interface is delivered with the amplifier.


CHARACTERISTICS

Interfaces: USB and hard-wire (DB25)
Rise time: 45µs
Noise equivalentcurrent: 30 p(ARMS) 
Gain, bandwidth and polarity control: 6 gain ranges; 4 bandwidths; polarity inversion
Auto-null function: up to 10V offset nulling



PRINCIPLES OF OPERATION

The TZA500 measures small currents e.g. optical power via a photodiode. Photodiodes are useful for power measurement in the visible and near infra-red due to their inherent sensitivity and speed of measurement.

Photodiodes produce a current which is proportional to the incident light power over a wide dynamic range.

The current is converted to a voltage through a precise transimpedance amplifier. This amplifier is very linear over the full measurement range of the device. The TZA500 has 6 gain ranges. The switch is a semiconductor device, free from degradation.

A unique feature of the TZA500 is the auto-null function. Further functions include signal inversion and bandwidth reduction. The analogue output signal is available at the BNC connector on the front panel an on the appropriate line on the interface port on the back panel.

The voltage generated is then converted to a digital value via a 12 bit A/D converter. This process and all calculations and communication with the PC are controlled by a microcontroller. The measurement process is started via a command over the USB interface (software trigger). Alternatively, a continuous measurement stream can be started which samples at 1.5 kS/s.

The measured photocurrent may then be read out from the USB port.


Schematic diagramme TZA500

FIELDS OF APPLICATION

These transimpedance amplifiers are particularly useful for the measurement of current from photodiodes. The output is a voltage linearly proportional to input current and thus, to input power in photodiode monitoring applications.

The fast response time at high signal-noise ratio makes this TZA series particularly useful in systems control feedback loops.

The high sensitivity and large dynamic range allow measurement of a wide range of optical sources such as lasers and LEDs via a variety of photodiodes for these applications such as Si and InGaAs.

The TZA500 series is insensitive to electromagnetic interference by design, an important factor when working in „dirty“ industrial environments. The proprietary auto-nulling function allows up to 10V of offset nulling. This is particularly useful for nulling dark current or for eliminating a DC signal component to concentrate on signal changes, such as in component burn-in and life-time testing.

- Input configuration: single ended, differential

- Input receptacle: BNC, BR2

- Bias: none, receptacle for external bias input

- Case: gull wing, lab style

 

BR2 connector, BR2 receptacle, bias input connector


What is a BR2 connector?

The outer dimensions and style of connection action of the BR2 connector are identical to BNC. However, instead of one centre pin, the BR2 has two inner pins beside each other (with the shielding braid around both of them). The use of BR2 connectors and shielded, twisted pair cable reduces noise considerably when measuring remote current sources in a noisy environment.


How can I measure a grounded source?

In order to measure a grounded source, the amplifier must have a single ended input configuration. You may use either the BNC or BR2 receptacle.


What is a differential input?

Often we think of a current source as having only one connection, however the other connection is just as important: it is the current return path. A differential input has an active amplifier input for both connection points to the current source. The outputs of these two amplifiers are then electrically subtracted. This has the effect of doubling the signal voltage (since the return path current is of opposite polarity), but cancels any noise components which were equal on both electrodes (“common mode” noise).

Spezifikationen TZA500