- #1
ajderoui
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I am having some issues designing a simple amplifier circuit and was wondering if anyone could help me. I feel like I am missing something fundamental, but can't seem to grasp it.
I'm using an AD826 dual operational amplifier using ±15 V supplies. I've breadboarded some very simple noninverting amplifiers with gain. Analog Devices recommends not using feedback resistors > 1 kΩ, so all of my feedback resistors are at that value. Lowering the value to 860 Ω allows me to add one stage before my problem occurs again but otherwise has little effect.
Individually each stage yields a clean output. The feedback resistance is 1 kΩ and the sense resistor is 330 Ω. I also have a 220 Ω input resistor. I'm using a 1 μF cap and a 0.01 μF cap for decoupling at each power supply rail of each op amp. There is no non-inverting amplifier (with gain) configuration shown in the datasheet: http://www.digikey.com/product-detail/en/AD826AR/AD826AR-ND/611660 however, the inverting amplifier configuration shown does the same thing (I am assuming the 50 Ω resistor to ground at the input is the equivalent circuit of the function generator and not a component of the circuit).
The problem is that once I connect enough stages in series, I see distortion in the output waveform (voltage output was less than half rail voltage) with a 150 kHz input sine wave (50 Ω generator output). A similar effect happens if I load down the output of a single stage - but I'm not sure how my chained circuits are loading each other down and how to remedy this problem.
Any advice would be much appreciated.
I'm using an AD826 dual operational amplifier using ±15 V supplies. I've breadboarded some very simple noninverting amplifiers with gain. Analog Devices recommends not using feedback resistors > 1 kΩ, so all of my feedback resistors are at that value. Lowering the value to 860 Ω allows me to add one stage before my problem occurs again but otherwise has little effect.
Individually each stage yields a clean output. The feedback resistance is 1 kΩ and the sense resistor is 330 Ω. I also have a 220 Ω input resistor. I'm using a 1 μF cap and a 0.01 μF cap for decoupling at each power supply rail of each op amp. There is no non-inverting amplifier (with gain) configuration shown in the datasheet: http://www.digikey.com/product-detail/en/AD826AR/AD826AR-ND/611660 however, the inverting amplifier configuration shown does the same thing (I am assuming the 50 Ω resistor to ground at the input is the equivalent circuit of the function generator and not a component of the circuit).
The problem is that once I connect enough stages in series, I see distortion in the output waveform (voltage output was less than half rail voltage) with a 150 kHz input sine wave (50 Ω generator output). A similar effect happens if I load down the output of a single stage - but I'm not sure how my chained circuits are loading each other down and how to remedy this problem.
Any advice would be much appreciated.