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Author Topic: solarcell preamp specs Patrick de Groot Expert Film Handler Posts: 161 From: Sprang-Capelle, Netherlands Registered: Apr 2001 posted 09-21-2001 03:34 AM                     Just curious, what are the specs of the output signal of the solarcells? And preamp used? What kind of pre-amp (input sensitivity, current, ...) should I use to amplify this signal properly? I'm asking this because I'm thinking about building some solarcell preamplifier myself (just for the fun of it, at least for now) I've already searched the forum, but I didn't found a clear answer.  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 09-21-2001 05:29 AM                        Build yourself an amplifier with an input sensitivity of -60db that has a 60-70 db gain with a flat frequency responce. In effect, a good microphone preamp. The cell has basically the same output characteristics as a microphone and you want to get the output level up to +4dbm or +8 dbm ...a 1 vpp signal into a 600 ohm load. There are some inexpensive preamp chips that'll do the trick very well.  |  IP: Logged Oscar Neundorfer Master Film Handler Posts: 275 From: Senoia, GA Registered: May 2000 posted 09-21-2001 06:53 AM                        A solar cell is basically a current output device, not a voltage output. It achieves its lowest distortion working into very low impedance loads on the order of a short. (Unfortunately, this produces very little voltage which a standard preamp needs in order to work.) Typically, the input impedance on solar cell preamps is 1500 Ohms or less. But even this is still quite high compared to what the cell would like to see. The problem with conventional circuits is that if you load the cell too much then there is little signal with which to work, and you have to increase the gain which increases noise. It is a definite tradeoff to get things just right. The best results are usually obtained with a virtual earth input circuit, such as that used in the Panastereo preamp, where the cell is connected directly to the inverting input of the opamp. This lets the cell deliver current into this input while producing very little voltage, and thus keeping distortion low. ------------------ Oscar Neundorfer Chief Engineer SMART Devices, Inc. oscar@smartdev.com  |  IP: Logged Patrick de Groot Expert Film Handler Posts: 161 From: Sprang-Capelle, Netherlands Registered: Apr 2001 posted 09-22-2001 10:09 AM                     would a preamp with an inputsensitivity of 0,2-2 mV do? amplifier factor adjustable from 150 to 1500 times. frequency range 50Hz-20kHz >>It achieves its lowest distortion working into very low impedance loads on the order of a short. If I understand this correctly: should the input sensitivity be as small as possible? (in this case 0,2 mV?) But why does the manual of the SMART730D says that it's input sensitivity is 10mV audio for full output?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-22-2001 10:24 AM                     Another device that makes a good preamp is the transonductance amplifiers when configured as a current to voltage converter.  |  IP: Logged

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