TW-MF2CAB Sglux

Application Note Multifunctional 2-Channel Amplifier Board Introduction In most applications of visible blind uv-detectors such as the twlux TW30-series only very small photocurrents are generated. These currents ranging from a microampere down to some picoampere cannot be measured by commonly available multimeters an amplifier is needed. We provide a small multifunctional amplifier board for developers to simplify and support application development. Note: The board is shipped without any photodiodes. Basics Photocurrents can be converted to voltages by transimpedance amplifiers (TIA) or switched integrating amplifiers (SIA). Our board utilizes the first type because it does not require digital timing signals. The complete schematic of our board is shown in Appendix B. For basic knowledge about this device please refer for instance to application notes for device OPA128 from TI at Application Note Multifunctional 2-Channel Amplifier Board Starting The index x in names relates to the channel number, for positions and pin numbers please refer to the picture on the right. Choose operation modes and configuration by setting jumpers MODx and STAGES refer to Appendix A, tables 2 and 3. Set required gains with jumpers GAINx and/or potentiometers RGAINx again refer to Appendix A, table 4. Connect arbitrary voltmeter(s) to screw terminals OUTx. Right pin ( 1) is the output, left pin ( 2) equals to GND. Connect the power supply to screw terminal PWR. For dual power supply use top terminal ( 3) for negative, middle ( 2) for GND and bottom terminal ( 1) for positive voltage. A single supply must be connected with positive pole to bottom pin ( 1) and supply GND to top pin ( 3), middle pin is left open. Note: In case of single supply there is a floating virtual ground on the middle terminal to which the inputs and outputs relate and which must not be connected to power supply GND. Adjust offsets for all channels. To do this shorten inputs for voltage amplifiers and leave inputs open (or insert photodiodes and darken them to compensate dark currents as well) for transimpedance stages. Now adjust the output voltages to 1mV or less by potentiometers POx. Connect photodiode(s) to either terminal INx or SOCKETx. The right pins ( 1) of screw terminals INx are the inputs, the left pins ( 2) equal to GND. If using the sockets the upper pinhole is the input and must be plugged with one photodiode pin in any case. Other pinholes are grounded and may be used as required. Polarity of the photodiodes within sockets depends only on desired output voltage polarity. Rev. 1.08 Page 2 5