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Wednesday, April 7, 2010

Simple Single Resistor Buffer

This is a simple design circuit for one method using a low-power, low-cost, closed-loop buffer including resistors and bypass capacitors. This circuit is based on CLC109 single chip IC. This is the figure of the circuit;

The CLC109's typical differential gain and phase are 0.7% and 0.03 degrees, respectively, while driving a 150 Ohms load. However, by adding a 1-kOhms pull-down resistor on the output pin, the respective numbers improve to 0.05% and 0.01 degrees, respectively. Thus, the cost of a single resistor brings an order-of-magnitude improvement and makes the differential gain and phase of the buffer comparable to much more expensive devices. However, if low power is a sensitive issue, you should carefully consider this method. Adding the resistor increases in the figure is typical supply current from 3.5 to 7.5 mA. This idea works equally well with video op amps.

Simple Microphone Mixer Circuit

This is simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs. This is the figure of the circuit;

In this circuit R1-R3 are level controls. R9 and R11 control bass and treble, respectively. Since the circuit draws such low current, two 9V batteries can be used for a power supply. This circuit is based on op amp 741 IC.

R1, R2, R3 1K 1/4W Resistor
R4, R5, R6 10K Logarithmic Pot
R7 1Meg 1/4W Resistor
R8, R10 10K 1/4W Resistor
R9, R11 100K Linear Pot
C1, C2, C5, C6 0.1uF Ceramic Disc Capacitor
C3, C4 22nF Ceramic Disc Capacitor
U1, U2 741 Op Amp
J1, J2, J3 Input Jacks Of Your Choice
MISC Board, Wire, Knobs, IC Sockets