Feature:  Common single-op-amp and dual-op-amp Screening circuit board, finished boards, the circuit board can judge whether the IC can be used for amplification, and can roughly judge the conversion rate of the chip.  IC1a in the circuit is connected to a multivibrator with a frequency of about 1Hz, and the OP Amp. to be tested is connected to a unity gain inverting amplifier working state. IC2 is an EX-OR gate, and its truth table is that the output is 1 when the two inputs are inverted. The original design D3 is green, because the solder mask of the printed board is green and not eye-catching, so it is changed to a yellow LED.   For chips with a low conversion rate, the status indicated by the LED is steady yellow, and red will flicker faintly. This can also be used to roughly judge the conversion rate of the chip. Because most of the motorcycle chips on the market use low conversion rate instead of high rate, it can also be judged whether the chip is cheap or not.     Therefore, after power-on, there are the following situations:  If OP Amp. is normal, points A and B of IC2 must be reversed, so C is 1, and it is still 1 after IC1b and 1d, so D3 of the yellow LED lights up, and the red LED goes out.  If the OP Amp. output is open, the C point of IC2 must always be 0, and it will become 1 after IC1c, so that the yellow LED is extinguished and the red LED D4 is lit.  If the internal short circuit of OP Amp. makes the output voltage fixed to positive or negative, the output of IC1c is also a 1Hz low-frequency square, and the red and yellow LEDs will flash alternately.  The actual test of low conversion rate such as: OP07, LM741, yellow is always on, red is slightly bright.  Test chips with high conversion rates, such as TL071, NE5534, MC34071 and other chips, the yellow is always on, and the red is off.  Single op amp model: LM741, LF356, NE5534, TL071, TL081, OP07 and other standard package single op amp.  Dual op amp model: LM358, NE5532, TL072, TL082, MC1458, RC4558, OP275, AD827 and other standard package dual op amps.  PCB size: 9.2 x 5.8 cm.  Power supply requirements: Voltage: 12VDC, current above 100mA.  Colour: black.  Material: plastic.     Package includes:  1 x Operational amplifier.  Only the above package content, other products are not included.     Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.