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I have a few TL071s would those work good. If not what would you suggest. Regards Dennis

I need a direct current linear amplifyer that with give me a gain of 10 from 1mv to 100 mv. Output inpedance > 10kohms VCC 5 volts Vee -5 volts So far I have tried both a 741 and 324 opamp and both have problems below 40mv. Any ideas would be appreciated Regards Dennis

MP The Only reason I changed the 180k to 100k was because both the intersil and maxim datasheets for the 7107 call for 100k resistor so I subed them into a prototype when I made it and it worked correctly so I left it in the final version. Regards Dennis

Moderator I posted this thread here instead of the long thread about the digital voltmeter in hopes that it may inspire someone to build it. If you choose to move it I understand after reading the entire thread I thought that someone might like to know that the schematic and project works correctly with the exception of replacing the 180k resistor with a 100k resistor. Here are some pictures of the finished board [img width=680 height=453] Again the only change I made to the board or components was using a 100k resistor instead of a 180k resistor Voltmeter works great and I plan on mounting it in a power supply soon Regards Dennis Waggoner

Im working on a function generator using the max038 IC Picture below \ The question is when I go to the board and auto generate the nets. Is there any tried and true way to place the components so as to minimize extranious routes along the circuit board Also below is a link to the above sch file if anyone is interested. http://www.wagsterstuff.com/photos/max038.zip Regards Dennis Waggoner

A TL071 is similar to an LF351 opamp since they both have difficulty with signals over 100kHz. 1MHz is a radio frequency so long wires can ruin the performance of your project. The parts on your perf board are very far apart causing series inductance in the long wires between parts. Capacitance between the long wires upsets the match of low-value capacitors and couples high frequency distortion products from wire to wire. Problems caused by long wires can be minimised if critical matched capacitors and resistors are mounted directly on the range switch. Thank you Thank you That kind of information I cannot get out of class. I will use that information to my advantage when I make the Max038 project. I will try to design and place the pots and switches directly on the pref boards and elimate all of the twisted wire leads. That should eliminate the inductance and also minimize capitance and thus reduce harmful resonance in the circuit. Tell me more tricks Please A resistive voltage divider usually sets a voltage for a high impedance input of a device. A series variable resistance usually needs another current-limiting resistor in series with it to set the maximum current from a source or to its load. Make perfect since now. You would not normally see a resistor in series in a voltage divider circuit. And you would have a resistor in series with a current limiting device because of the input current requirements of the device. Beside there is no signal present on pins 1 and 12 of the 8038 so why would you need voltage (or signal) that a voltage divider would give you. AH. I am only a grasshopper (50 year old grasshopper) but I am learning to hop and spit. Regards Dennis Waggoner

Actually I replaced it with the TL071 ? I did look at the datasheets and knew distortion increased over 200khz or so. I just wondered if the ringing would be considered part of the THD or something else. Thanks for the welcome. I do plan on a project using the max038 chip along with the buf634 amp. Just putting together the project now doing more research on shielding the circuit and checking components (mainly caps) requirements. I also plan on using the circuit shown in the diy kit101 found readily available as a pdf on the web. One thing I did find after breadboarding the circuit was that all of the pots in the circuit needed to be current limiting except the output to the opamp which needs to be a voltage divider. Im basically a neophyte at Electronics with on a few hours toward my degree. I have difficulity understanding some circuts and when the pot should be connected as Voltage dividers and when they should be connected a series variable resistors. Regards Dennis Waggoner

I built the Function Generator listed in the Projects using the ICL8038 Chip and have some problems with distortion at the High end of the frequency range 1Mhz. Below are a couple of pictures of the completed project and also a screenshot of the Scope image showing the ringing at the voltage peaks. Does anybody know what causes this. [img width=680 height=453] [img width=680 height=453] Regards Dennis Waggoner