Classification of bipolar integrated circuits

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Classification of bipolar integrated circuits

Bipolar integrated circuits were developed based on silicon planar transistors. The earliest is bipolar digital logic integrated circuits. In the development of digital logic integrated circuits, many different types of circuit forms have appeared. Common bipolar integrated circuits can be classified as follows.

The DCTL circuit is the first type of bipolar digital logic integrated circuit, which is impractical due to the serious "current snatch" problem (see resistor-transistor logic circuits). RTL circuit is the first bipolar integrated circuit with practical value. Early digital logic systems used RTL circuits, which later limited the switching speed due to the presence of resistors in the base input loop. In addition, the anti-interference performance of the RTL logic circuit is poor, and the load cannot be much when used, so it is eliminated. The resistance-capacitance-transistor logic circuit (RCTL) is proposed in order to improve the switching speed of the RTL circuit, that is, a capacitor is connected in parallel with the resistance of the RTL circuit. In fact, RCTL circuits have not been developed. The DTL circuit is proposed after the RTL circuit to improve the anti-interference ability of the logic circuit. The DTL circuit uses level-shifting diodes on the line, and the anti-interference ability can be adjusted by the number of level-shifting diodes. The level-shifting diode of the commonly used DTL circuit is formed by connecting two silicon diodes in series, and its anti-interference ability can be improved to about 1.4 volts (see diode-transistor logic circuit). HTL circuits are derived on the basis of DTL circuits. The HTL circuit uses a reverse-connected Zener diode instead of the level-shifting diode of the DTL circuit to increase the threshold of the circuit to about 7.4 volts (see High-threshold logic circuits). Variable threshold logic (VTL) is another variant of the DTL circuit family. Threshold logic (TLC) is a general term for HTL and VTL logic circuits. The TTL logic circuit evolved from the DTL logic circuit and was successfully developed in 1962. In order to increase the switching speed and reduce the power consumption of the circuit, the TTL circuit has undergone three generations of circuit form improvements in the line structure (see transistor-transistor logic circuits).

The above are all saturated circuits. While further exploring to increase the switching speed of the saturated circuit, it is found that the storage effect of the excess carriers of the transistor is a very important obstacle. The storage phenomenon is essentially caused by the excess carriers in the switching process of the circuit. To increase the switching speed of the circuit, in addition to reducing the PN junction capacitance of the transistor, or trying to shorten the life of the excess carriers, it is necessary to reduce and eliminate the phenomenon of carrier storage in the transistor. In the late 1960s and early 1970s, people began to use the well-known Schottky effect in integrated circuits. A Schottky barrier diode is prepared on the TTL circuit, and it is connected in parallel to the base and collector of the original transistor, so that the switching time of the transistor is shortened to about 1 nanosecond; the TTL gate with Schottky barrier diode clamping The average transmission delay time of the circuit is 2 to 4 nanoseconds.

Schottky barrier diode-transistor-transistor logic (STTL) belongs to the third generation of TTL circuits. It uses a Schottky barrier diode clamping method on the line to make the transistor in a critical saturation state, thereby eliminating and avoiding the carrier storage effect. At the same time, the introduction of a transistor shunt at the base of the TTL circuit and the inverter output stage inverter can improve the characteristics of the NAND gate. The triode has a Schottky barrier diode, which can avoid entering the saturation region and has high-speed performance. The output tube plus a shunt can maintain the anti-saturation level of the output stage inversion. This type of bipolar integrated circuit is no longer a saturated integrated circuit, but another type of anti-saturated integrated circuit with a much faster switching speed.

Emitter-coupled logic (ECL) is a current-mode logic (CML). This is a current switching circuit. The transistor of the circuit works in a non-saturated state, and the switching speed of the circuit is several times faster than the usual TTL circuit. The ECL logic circuit increases the circuit switching speed to about 1 nanosecond, far exceeding the TTL and STTL circuits. The emergence of ECL circuits has brought bipolar integrated circuits into the ultra-high-speed circuit range.

Integrated injection logic (I2L), also known as merged transistor logic (MTL), was developed in the 1970s. Among bipolar integrated circuits, I2L circuits have the highest integration density.

The three-layer structure logic circuit (3TL) is an improvement on the basis of I2L circuits in China in 1976. It is named after a three-layer structure. 3TL logic circuit uses NPN tube as the current source, and the output tube uses metal as the collector (PNM), which is different from the I2L structure.

Multiple logic circuits (DYL) and double-layer logic circuits (DLL) are new logic circuits successfully developed in China in 1978. The DYL logic circuit is a linear AND-OR gate, which can simultaneously realize switching logic and linear logic processing functions. The DLL circuit implements the logic function of the circuit through the internal conversion of the dual information of the ECL and TTL logic circuits.

In addition, during the development of bipolar integrated circuits, there were many other types of circuits. For example, emitter function logic (EFL), complementary transistor logic (CTL), radiation-resistant complementary constant current logic (C3L), current staggered logic (CHL), tri-state logic (TSL), and non-threshold logic Circuit (NTL), etc.