The equation for the output Vo =Input voltage * Gain = Vi * A = Vi * ( 1+ R2/ R3).R2 and R3 resistors form feedback loop for the non- inverting amplifier of op-amp.Amplified output is listened through the small speaker connected at the output.R1 and C1 form a high pass filter for cutting of DC signal from microphone.Microphone output signal is given as input to op-amp for amplification.In the above microphone amplifier circuit the op-amp acts as a Non-Inverting Amplifier (Since input is given to Non-inverting terminal of op-amp. And to understand the working of device we will use a single op-amp to construct a simple microphone pre-amplifier circuit as given below. The two op-amps in the chip can be used to design most of op-amp based circuits like voltage follower, comparator, differential amplification and mathematical operations.
This device is used to be popular a decade ago but at present there are many op-amp chips which are more accurate and more efficient.īefore going for application of the device let us see the internal connection of two op-amps in the device as shown below. Also the device has offset pins for making the output more accurate which is a must in some applications. More over the two op-amps can perform two different functions at a time which comes in handy in applications. Large common mode and differential voltage rangeĪs mentioned earlier LM747 IC consists of two general purpose operational amplifiers and so the chip can be used to design any op-amp circuits like comparator, differential amplification or mathematical operations.LM747 Features and Electrical characteristics The device is available in many packages and can be chosen depending on requirement. Offset null pin used to eliminate the offset voltage and balance the input voltages for op-amp 2 Offset null pin used to eliminate the offset voltage and balance the input voltages for op-amp 1 LM747 is a 14 pin device as shown in above LM747 pinout and description for each pin is given below.Ĭommon negative supply voltage for both Op-amps The chip is short circuit protected and the internal frequency compensation ensures stability without external components.
Otherwise, their operation is completely independent. The two amplifiers share a common bias network and power supply leads. The prefix LM stands for linear monolithic, referring to the analog components integrated onto a single piece of silicon.
#OP AMP OFFSET COMPENSATION CIRCUIT BASED ON NULL PINS SERIES#
The ‘LM xx’ series are integrated circuits designed by National Semiconductor. LM747 is a general purpose dual operational amplifier IC and is a member of ‘LM xx’ family.
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