Converts current to voltage - ideal for PMTs and photodiodes
Low noise and wide dynamic range
Wide bandwidth - DC to 100 kHz
The 70710 is a low noise current-to-voltage amplifier, designed for photomultiplier tubes or photodiodes operating in the photovoltaic mode. It converts the low current output from many of our detectors, to a voltage signal for the Merlin™ Digital Lock-in Radiometry System.
This preamplifier converts the current from the following Oriel Detectors to a voltage signal, for readout.
Oriel Silicon Detectors
One of the most practical features of the 70710 is that it has six switchable amplifier selections, 104, 105, 106, 107, 108 and 109 volts per ampere. The 70710 also has a three position time constant switch. Standard BNC input and output connectors facilitate connection to other devices.
The preamplifier bandwidth depends on the gain setting and the selected time constant. The following table shows the bandwidth values at three gain settings.
| Time Constant | Gain | ||
|---|---|---|---|
| 104 | 106 | 109 | |
| MIN | 100 kHz* | 80 kHz | 80 Hz |
| MED | 100 kHz | 1 kHz | 1 Hz |
| MAX | 1 kHz | 10 Hz | 0.01 Hz |
The 70710 has wide dynamic range and linearity. The volts per ampere conversion ratio is determined by the switch setting. Changing the switch changes the feedback resistor. The input impedance, i.e. the apparent resistance, which the amplifier displays at its input, equals the feedback resistance divided by the gain of the operational amplifier (which is at least 150,000) plus a 1,200 ohm isolation resistor at the amplifier’s input. A feedback resistor of 106 ohm corresponds to a conversion ratio of 106, etc. The input impedance is then 106/150,000 or about 7 ohms plus the 1,200 ohm isolation resistor. Even at the 109 V/A setting, the input impedance is only about 8,000 ohms. These relatively low impedances are essential for obtaining a wide linear dynamic range from photodiodes.
The 70710 must be powered by an external ±15 V supply such as our model 70703 . We provide a power cable with banana jack terminals for connection to the 70703 or other ±15 V source.