If you take, for example, the transistor MJE3055T. It has a maximum current 10a, and the gain is only about 50, respectively, so that it opens completely, it needs to pump about two hundred perm at the database. The usual conclusion of the MK will not pull so much, and if you fall in between the transistor with a challenge (some BC337), which can drag these 200mA, then easily. But it is so that I knew. Suddenly, it will have to make control of the girlish trap - it will be useful.

In practice, ready-made transistor assemblies. Externally from the ordinary transistor is no different. The same body, the same three legs. That's just the power in it painfully dofiga, and the control current microscopic :) In the prices, they usually do not bother and write simply - the transistor of the Darligntone or the composite transistor.

For example, a para BDW93C. (NPN) and BDW94S. (PNP) Here are their internal structure from datasheet.

Moreover, exist assembling Darlington. When in one case pack at once several. An indispensable thing when you need to steer some powerful LED table or stepper engine (). Excellent example of such an assembly - very popular and easily accessible ULN2003.able to drag up 500 ma for each of its seven assemblies. Outputs can be turn on parallelTo increase the limit. Total one ULN can be dragged through itself 3.5a, if you post all its inputs and outputs. What makes me pleases - getting opposite the entrance, very convenient to plant a fee for it. Straight

In the datashet, the internal structure of this chip is indicated. As you can see, there are also protective diodes here. Despite the fact that the operational amplifiers are drawn, here is the output of an open collector. That is, he knows how to close only to Earth. What becomes clear from the same datashet if you look at the structure of one valve.

Darlington), are often composite elements of amateurs structures. As is known, with such an inclusion, the gain of the current, as a rule, increases ten times. However, it is not always possible to achieve a significant reserve of operability for the voltage affecting the cascade. Flow amplifiers consisting of two bipolar transistors (Fig. 1.23) often fail when exposed to pulsed voltage, even if it does not exceed the value of the electrical parameters specified in the reference literature.

With this unpleasant effect you can fight in different ways. One of them - the simplest - is the presence of a transistor with a large (several times) reserves of a resource on the voltage collector-emitter. The relatively high cost of such "high-voltage" transistors leads to an increase in the cost of the design. You can, of course, purchase special composite silicon in one case, for example: KT712, CT829, KT834, KT848, KT852, KT853, KT894, KT897, KT898, KT973, etc. This list includes powerful and middle power Instruments developed by almost the entire spectrum of radio engineering devices. And you can use the classic one with two parallel-enabled field transistors of the KP501B type - or use the devices KP501A ... B, KP540 and others with similar electrical characteristics (Fig. 1.24). At the same time, the shutter output is connected instead of the VT1 base, and the source output is instead of the VT2 emitter, the flow output is instead of the united collectors VT1, VT2.

Fig. 1.24. Replacing the field transistors of the composite transistor

After such an uncomplicated refinement, i.e. Replacing nodes in electrical circuits, universal use, current on transistors VT1, VT2 does not fail even at 10 times and more voltage overload. Moreover, the restrictive resistor in the VT1 shutter circuit is also increased several times. This leads to the fact that they have a higher input and, as a result, withstand overload with a pulse character of controlling this electronic node.

The gain of the current cascade obtained is at least 50. Increases directly proportional to the increase in the supply voltage of the node.

VT1, VT2. In the absence of discrete transistors of the type KP501A ... in can be used without losing the quality of the device, use the microcircuit 1014ct1B. In contrast, for example, from 1014T1A and 1014ct1B, this can withstand higher overloads on the applied pulsed voltage - up to 200 in constant voltage. COFCOLOGE Turning on the transistors of the microcircuit 1014ct1a ... 1014K1V is shown in Fig. 1.25.

As in the previous embodiment (Fig. 1.24), include in parallel.

Cocolevka field transistors in the microcircuit 1014ct1a ... in

The author tried tens of electronic nodes included by software. Such nodes are used in amateur structures as current keys in the same way as composite transistors included software. To the features of field transistors listed above, you can add their energy efficiency, since in the closed state due to the high input, they practically do not consume current. As for the value of such transistors, today it is almost the same as the cost of the type of mediterranean type transistors, (and similar to them), which are used as a current amplifier to control the load devices.

The amplifier is called this, not because of his author Darlington, but because the outlet stage of the power amplifier is built on Darlington (composite) transistors.

For reference : The two transistors of the same structure are connected in a special way for high gain. Such a connection of transistors forms a composite transistor, or the Darlington transistor - by the name of the inventor of this circuit solution. Such a transistor is used in the schemes of working with large currents (for example, in the diagrams of voltage stabilizers, output cascades of power amplifiers) and in the input cascades of amplifiers, if it is necessary to provide a large input impedance. The composite transistor has three outputs (base, emitter and collector), which are equivalent to the conclusions of the usual single transistor. The gain coefficient of a typical compound transistor, in powerful transistors ≈1000 and in low-power transistors ≈50000.

Advantages of transistor Darlington

High gain coefficient.

The Darlington CHEMA is manufactured in the form of integrated circuits and at the same current, the working surface of silicon is less than that of bipolar transistors. These schemes are of great interest at high voltages.

Disadvantages of composite transistor

Low speed, especially the transition from the open state in the closed. For this reason, composite transistors are used primarily in low-frequency key and amplifying schemes, at high frequencies, their parameters are worse than a single transistor.

Direct voltage drop in the transition of the base-emitter in the Darlington scheme is almost twice as many than in the usual transistor, and is about 1.2 - 1.4 V. for silicon transistors

A large saturation voltage collector-emitter, for a silicon transistor about 0.9 V for low-power transistors and about 2 B for high power transistors.

Schematic diagram of UNG.

The amplifier can be called the cheapest option to independently construct a subwoofer amplifier. The most valuable in the scheme is the weekend transistors, the price of which does not exceed $ 1. In theory, this amplifier can be collected for $ 3-5 without a power supply. Let's make a small comparison, which of the chip can give a power of 100-200 watts to a load of 4 ohms? Immediately in the thoughts are famous. But if we compare prices, then Darlington scheme and cheaper and more powerful TDA7294!

The chip itself, without component components cost $ 3 at least, and the price of the active components of the Darlington scheme is not more than $ 2-25! Moreover, the Darlington scheme by 50-70 watt is more powerful than TDA7294!

With a load of 4 Ohm, the amplifier gives 150 watts, it is the cheapest and good version of the subwoofer amplifier. In the amplifier scheme used inexpensive rectifier diodes that can be reached in any electronic device.

The amplifier can provide such power due to the fact that it is compiled transistors that are used at the output, but if desired, they can be replaced by ordinary. It is convenient to use the complementary pair of CT827 / 25, but of course the power of the amplifier will fall up to 50-70 watts. Domestic-CT361 or CT3107 can be used in the differential cascade.

The full analogue of the TIP41 transistor is our KT819A, this transistor is used to enhance the signal from diffracts and the offset of the outputs. Emitter resistors can be used with a capacity of 2-5 watts, they are for the protection of the output cascade. Read more about TIP41C transistor technical characteristics. Datasheet for TIP41 and TIP42.

P-N-N transition material: Si

Transistor structure: NPN

Limit Permanent Scatter Power Collector (PC) Transistor: 65 W

Limit constant pressure Collector-base (UCB): 140 V

Limit constant voltage collector-emitter (UCE) of the transistor: 100 V

Limit constant voltage Emitter base (UEB): 5 V

Limit d.C. Transistor collector (IC MAX): 6 A

Limit p-N temperature Transition (TJ): 150 C

Boundary frequency of the current transmission coefficient (FT) of the transistor: 3 MHz

- Capacity of the collector transition (CC): PF

Static current transmission coefficient in a circuit with a common emitter (HFE), MIN: 20

Such an amplifier can be used both as a subwoofer and broadband acoustics. The characteristics of the amplifier are also quite good. With a load of 4 ohms, the output power of the amplifier is about 150 watts, with a load in 8 Ohm power 100 watts, the maximum power of the amplifier can reach 200 watts with +/- 50 volts.

When designing radio-electronic devices schemes, it is often desirable to have transistors with parameters better than those models that offer firms manufacturers of radio-electronic components (or better than to implement the available technology of manufacturing transistors). This situation is most often found when designing integrated circuits. We usually require a greater gain in current gain. h. 21, greater input resistance value h. 11 or less output conductivity h. 22 .

Improve transistor parameters allow various schemes of compound transistors. There are many possibilities to implement a composite transistor from field or bipolar transistors of various conductivity, while improving its parameters. Darlington scheme received the greatest distribution. In the simplest case, this is the connection of two transistors of the same polarity. An example of the Darlington scheme on NPN transistors is shown in Figure 1.

Figure 1 Darlington diagram on NPN transistors

The diagram is equivalent to a single NPN transistor. In this circuit, the Emitter current of the transistor VT1 is the current of the VT2 transistor base. The current of the collector of the composite transistor is determined mainly by the current transistor VT2. The main advantage of the Darlington scheme is the high value of the current gain coefficient h. 21, which can be approximately defined as a work h. 21 incoming transistors:

(1)

However, it should be borne in mind that the coefficient h. 21 strongly depends on the current collector. Therefore, with small values \u200b\u200bof the current collector of the transistor VT1, its value can significantly decrease. Example addiction h. 21 from the current collector for different transistors is shown in Figure 2

Figure 2 Dependence of the gain of transistors from a collector current

As can be seen from these graphs, the coefficient h. 21E practically does not change only in two transistors: domestic CT361B and foreign BC846A. In other transistors, the current gain is significantly dependent on the collector current.

In the case when the base current of the VT2 transistor is sufficiently small, the VT1 transistor collector current may be insufficient to provide the required current gain coefficient h. 21. In this case, increasing the coefficient h. 21 and, accordingly, the decrease in the current of the composite transistor can be achieved by increasing the current of the collector of the VT1 transistor. To do this, between the base and emitter of the VT2 transistor include an additional resistor, as shown in Figure 3.

Figure 3 of the composite transistor of Darlington with an additional resistor in the emitter chain of the first transistor

For example, we define the elements for the Darlington scheme, assembled on the BC846A transistors let the VT2 transistor current be 1 mA. Then his base current will be equal to:

(2)

With such a current, the gain coefficient h. 21 drops sharply and the total current gain can be significantly less than the calculated one. Increased current collector VT1 transistor with a resistor, you can significantly win in the value of the total gain. h. 21. Since the voltage based on the transistor is a constant (for a silicon transistor u. BE \u003d 0.7 V), then we calculate according to the law of Ohm:

(3)

In this case, we have the right to expect a current gain to 40000. It is thus many domestic and foreign superbett transistors, such as KT972, CT973 or CT825, TIP41C, TIP42C. The Darlington scheme is widely used in the output cascades of low frequency (), operating amplifiers, and even digital, for example,.

It should be noted that the Darlington scheme has such a disadvantage as increased voltage U. CE If in conventional transistors U. Ke is 0.2 V, then in a composite transistor, this voltage increases to 0.9 V. This is due to the need to open the transistor VT1, and for this, the 0.7 V voltage should be applied to its base (if we consider silicon transistors).

In order to eliminate the specified disadvantage, a circuit of a composite transistor on complementary transistors was developed. In the Russian Internet, she received the name of the scheme of Shiklai. This name came from the book by Titz and Shanka, although this scheme had previously had a different name. For example, in Soviet literature, it was called a paradox pair. In the book of V.E.Hhelin and V.Kholms, a composite transistor on complementary transistors is called the White scheme, so we will be called it simply a composite transistor. The circuit of the composite PNP of the transistor on complementary transistors is shown in Figure 4.

Figure 4 Composite PNP transistor on complementary transistors

In the same way, the NPN transistor is formed. The circuit of the compound NPN of the transistor on complementary transistors is shown in Figure 5.

Figure 5 of the composite NPN transistor on complementary transistors

In the first place in the first place is the book of 1974 of the publication, but there are books and other publications. There are foundations that do not stir for a long time and a huge number of authors who simply repeat these bases. You need to say clearly! For all the time of professional activity, I met less than ten books. I always recommend learn an analog schema engineering from this book.

Date of the latest file update 06/18/2018

Literature:

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In integrated circuits and discrete electronics, two types of composite transistors received great distribution: according to the Darlington and Shiklaya scheme. In micromogenic schemes, for example, the input cascades of operating amplifiers, compound transistors provide large input resistance and small input currents. In devices operating with large currents (for example, power stabilizers or output storage stabes) to increase the efficiency, it is necessary to provide a high gain of powerful transistors.

Shiklai scheme implements powerful p-N-P transistor with a large gain with low-power p-N-P transistor with small IN and powerful n-P-N transistor ( figure 7.51). In integrated circuits, this inclusion is implementing high p-N-P horizontal transistor p-N-P transistor and vertical n-P-N transistor. Also, this scheme is used in powerful two-stroke output cascades when the output transistors of the same polarity are used ( n-P-N).

Figure 7.51 - Composite p-N-P Transistor Figure 7.52 - Composite n-P-N According to the scheme of Shiklai Transistor according to the Darlington scheme

Shiklai or complementary transistor Darlington transistor behaves like a transistor p-N-P type ( figure 7.51) with a large current gain coefficient

Input voltage Identically solitary transistor. Saturation voltage is higher than that of a single transistor to the voltage drop in the emitter transition n-P-N transistor. For silicon transistors, this voltage is the order of one volt, in contrast to the share of Volta of a single transistor. Between the base and emitter n-P-N The transistor (VT2) is recommended to include a resistor with a small resistance to suppress unmanaged current and improving thermal resistance.

The Darlington transistor is implemented on unipolar transistors ( figure 7.52.). The current gain is determined by the product of the coefficients of the components of the transistors.

The input voltage of the transistor according to the Darlington scheme is twice as much as a single transistor. Saturation voltage exceeds the output transistor. Input resistance of the operational amplifier at

.

Darlington scheme is used in discrete monolithic pulsed transistors. On one crystal, two transistors are formed, two shunt resistors and a protective diode ( figure 7.53.). Resistors R.1 I. R.2 suppress amplification coefficient in low current mode, ( figure 7.38), which provides a small value of unmanaged current and increasing the operating voltage of the closed transistor,

Figure 7.53 - Electrical circuit Monolithic Pulse Transistor of Darlington

The R2 resistor (about 100 ohms) is formed in the form of a technological shunt, like shunts of the cathode transition of thyristors. For this purpose, when forming - an emitter using photolithography in certain local areas, an oxidic mask is left in the form of a circle. These local masks do not allow to diffuse a donor impurity, and under them remain p-columns ( figure 7.54.). After metallization over the entire Emitter area, these columns are distributed resistance R2 and a protective diode D ( figure 7.53.). The protective diode protects emitter transitions from breakdown when reformed collector voltage. The input power of the transistor consumption according to the Darlington scheme is one and a half two orders of magnitude lower than that of a single transistor. The maximum frequency of switching depends on the limit voltage and current of the collector. Talk transistors successfully operate in pulse converters to the frequencies of about 100 kHz. A distinctive feature of the monolithic transistor of Darlington is a quadratic gear ratio, since IN-the ampere characteristic is linearly increasing with an increase in the collector current to the maximum value,