According to the parameters of integrated operational amplifiers, integrated operational amplifiers can be divided into the following categories:
General purpose operational amplifier is designed for general purpose. The main characteristics of this type of device are low price, large product volume and wide range, and its performance indicators can be suitable for general use. Examples μA741 (single op amp), LM358 (dual op amp), LM324 (four op amp) and LF356 with field effect tube as the input stage all belong to this type. They are currently the most widely used integrated operational amplifiers.
The characteristic of this kind of integrated operational amplifier is that the differential mode input impedance is very high, the input bias current is very small, generally rid>1GΩ~1TΩ, IB is several picoamps to dozens of picoamps. The main measure to achieve these indicators is to take advantage of the high input impedance of the field effect tube, and use the field effect tube to form the differential input stage of the operational amplifier. Using FET as the input stage not only has high input impedance, low input bias current, but also has the advantages of high speed, broadband and low noise, but the input offset voltage is relatively large. Common integrated devices include LF355, LF347 (four operational amplifiers) and higher input impedance CA3130, CA3140, etc.
In precision instruments, weak signal detection and other automatic control instruments, it is always hoped that the offset voltage of the operational amplifier should be small and not change with temperature changes. The low temperature drift operational amplifier is designed for this. At present, the commonly used high-precision, low-temperature drift operational amplifiers include OP07, OP27, AD508 and the chopper-stabilized zero-drift device ICL7650 composed of MOSFETs.
In fast A/D and D/A converters and video amplifiers, the conversion rate SR of the integrated operational amplifier must be high, and the unity gain bandwidth BWG must be large enough, like general-purpose integrated operational amplifiers, which are not suitable for high-speed applications. Occasional. The main feature of high-speed operational amplifiers is a high conversion rate and wide frequency response. Common operational amplifiers include LM318, μA715, etc., with SR=50~70V/us and BWG>20MHz.
Since the biggest advantage of electronic circuit integration is to make complex circuits small and light, with the expansion of the application range of portable instruments, it is necessary to use low power supply voltage and low power consumption operational amplifiers. Commonly used operational amplifiers are TL-022C, TL-060C, etc., whose working voltage is ±2V~±18V, and the current consumption is 50~250μA. At present, the power consumption of some products has reached the μW level. For example, the power supply of the ICL7600 is 1.5V and the power consumption is 10mW, which can be powered by a single battery.
The output voltage of the operational amplifier is mainly limited by the power supply. In an ordinary operational amplifier, the maximum output voltage is generally only tens of volts, and the output current is only tens of milliamps. If you want to increase the output voltage or increase the output current, an auxiliary circuit must be added outside the integrated operational amplifier. The high-voltage and high-current integrated operational amplifier can output high voltage and high current without any additional circuits. For example, the power supply voltage of D41 integrated operational amplifier can reach ±150V, and the output current of μA791 integrated operational amplifier can reach 1A.
In the use of instruments and meters, the problem of range will be involved. In order to obtain the output of a fixed voltage, the amplification factor of the operational amplifier must be changed. For example: an operational amplifier has the amplification factor of 10 times, and the input signal is 1mv, the output voltage When the input voltage is 0.1mv, the output is only 1mv. In order to get 10mv, the magnification must be changed to 100. The program-controlled operational amplifier is produced to solve this problem. For example, PGA103A, by controlling the 1, 2 feet Level to change the magnification.