Traditional op amps drive power amplifiers, which are difficult to increase due to the limitations of the op amp voltage. The power amplifier uses the voltage conversion current mode to directly drive the power amplifier tube for power amplification, so the output power mainly depends on the final stage power amplifier tube and the power amplifier power supply, and the speaker has no on/off impact sound. The whole machine does not add any compensation capacitors, the original taste, the phase shift is small. Since the op amp is used for constant current amplification, it is convenient to replace the op amps with different performances, and the sound has more choices. This article designed a simple and practical power amplifier driven by an op amp.
The circuit is shown in Figure 1. IC1 and T1, IC2 and T2 form a current negative feedback absorption constant current source, which are responsible for the voltage and current conversion amplification of the positive and negative half cycles of the audio signal, respectively, so that the T3 and T4 base currents are only affected by IC1. IC2 input voltage control, that is, as long as the op amp input is a constant voltage value, the current flowing through the collectors of the final tubes T3 and T4 is also a constant value. W1, W2 (multi-turn potentiometer) are used to adjust the quiescent current and output zero point of T3 and T4 respectively. IC3 and R1, R2 and R5 form a quasi-current negative feedback circuit. As long as the resistance values ​​of R3, R4 or R2 and R6 are changed accordingly, Can change the gain size. The power amplifier protection circuit (Fig. 2) adopts the method of cutting off the total power supply. The advantage is that when the power amplifier fails, not only the speaker but also the last stage tube is protected. The working principle is: When the power is turned on, T6 is electrically turned on, J is self-protected, and the power supply is kept on. When the zero-point DC component of the power amplifier output is greater than ±0.24V, IC4 or IC5 outputs a high level, so T5 is saturated and turned on, T6 is turned off, relay J is released, and the total power is cut off, thereby realizing the protection function for the speaker and the power amplifier tube. .
High performance amplifier driven by op amp

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The debugging of this machine is relatively simple. First adjust W1 and W2 to the minimum position, then slowly adjust W1 and W2 to make the voltage drop on R8 and R7 to 40mV (200mA). Measure the output point and fine tune W1 or W2 to control the output point voltage below 5mV. Then preheat for half an hour, then re-adjust it, you can access the speaker audition. Subjective evaluation, the amplifier has a high signal-to-noise ratio, full bass, flexibility, and high-pitched sound.
The op amp adopts dual op amps such as NE5532 or AD827, T1 and T2 select power tube 2SB647, 2SD667, etc. The final stage power amplifier tube can use three-way paired tube 2SC2922, 2SA1216 or 2SC3281, 2SA1302 and other audio pair tubes, and the resistor uses 1/4W metal. Membrane resistance.


The CH0004 is a self-contained Battery Charger/conditioner mounted in a ruggedized environmentally resistant case, which provides a reliable and consistent recharge of one or two batteries simultaneously. The CH0004 auto senses battery type to assure proper charge profile.

Unattended Charging

• Smart charge modules that detect open or shorted cells. If a defective cell is detected the CH0004 will not start charge cycle

• No programming or special instruction set to achieve safe and complete recharge of battery

• In no event will a battery be overcharged using the smart charging

techniques of the CH0004

Wide Range Input Voltage

• Allows operation from nearly any AC or DC power source likely to be encountered worldwide

 Conditioning Cycle

• Automatic discharge/recharge function included. The conditioning cycle can be activated individually per battery at operator`s option

Recharge Each String of Cells

• To assure a positive recharge of the battery each individual string of cells in the battery is recharged independently

Any combination of the following batteries: BB-390/U - (NiMH), BB-590/U - (NiCd), BB-2590 / UBI-2590 (UBBL02) / MRC-2590 /UBBL09 / UBI-2590 SMBus (UBBL10) -Lithium-Ion (Li-ion)



Military Battery Charger

Military Battery Charger,Battery Charger,Nimh Battery Charger,Lithium Battery Charger

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