DE968184C - Transistor amplifier with transmission coupling - Google Patents

Description

ISSUED JANUARY 23, 1958

NII0I7VIII aj21 a *

The invention relates to a transistor amplifier with two transistors, in which the Collector circuit of the first transistor via a matching transformer with the emitter circuit of the second transistor lying in base circuit is coupled.

It is known that in transistors, in general the collector direct current changes quite strongly with the temperature. To this un-

To suppress desired change, it is also known, if necessary, in the emitter circuit take up resistance decoupled for the signal frequencies. On the other hand, the aspirations go to make the matching transformer as small as possible. However, this is opposed by the fact that the DC currents flowing through the transformer windings create an undesirable premagnetization of the Can bring about transmission core.

It is. further known at the Aosgangisifcrainisiformator of a tube amplifier miitfealis one of an auxiliary winding flowing through a direct current an illustration of direct current fore-nagging to reach. The circle of this auxiliary winding sail only serves to carry direct current; for alternating current the circle should be open and not evoke any belief. He must therefore have an enitkoppelungBdmpediaiiz contain.

The invention now relates to circuit arrangements in which both influences with simple Funds are canceled; these indicate the

709 86W24

times on that the transformer with two secondary windings is provided, which together with a stabilization resistor from the Emittorgleidhstrom flow through this second transistor in the, series, while only one of these secondary windings, expediently the winding with the lowest number of turns, via a coupling capacitor between the emitter or base electrode of the second transistor for the signal voltage is effective.

The invention is explained in more detail using exemplary embodiments.

Fig. Ι shows the basic circuit diagram of the invention; Fig. 2 shows a completed circuit diagram after

»5 Fig-i;

Fig. 3 shows a variant of Fig. 2; Fig. 4 shows a variant of Fig. 3, and FIG. 5 shows another variant of FIG. 3. The amplifier according to FIG. 1 has a first one

ao transistor 1 and. a second transistor 2, expediently both surface transistors. The collector circuit of the transistor 1 is by means of a matching transformer 3 matched to the emitter circuit of transistor 2. Signals from a source 4 eras produce signals that have been amplified in this way a load 5. According to the invention, the transformer 3 has two primary winding 6 as well Secondary windings 7 and 8. The emitter direct current of transistor 2 flows through from the positive terminal the supply source, the series connection of these windings 7 and 8 and 'a stabilization resistor 9, which thus stabilizes the transistor 2, while because of the coupling capacitor 10 only the winding 7 for alternating voltage between the emitter and base electrodes of the Transistor 2 is effective.

This ensures that the opposite Meaning with the correct choice of the number of turns of approximately equal direct currents flowed through windings 6 or 7 and 8 practically no direct current bias of the Cause transformer 3 and on the other hand, the transistor 1 is properly matched to the transistor 2 can be. If the winding 8 is also made of thinner wire with a high inherent resistance is not only possible to save space, but also the resistor 9 be dispensed with.

In the construction of the amplifier according to FIG. 2, the two transistors 1 and 2 are made of one single voltage source 12 is fed, and the base bias is by means of the voltage divider 13, 14 generated collectively. The transistor 1 is stabilized by means of a resistor 16 decoupled by the capacitor 15; at the Transistor 2, this is achieved in accordance with FIG. 1 by means of resistor 9 and capacitor 10. If necessary, at least one resistor can be used for further stabilization Have temperature dependence.

Fig. 3 shows a modification. the circuit according to FIG. 2, in which the resistor 9 is replaced by a resistor 9 'between the secondary winding 8' and the supply source 12; the capacitor 10 'is connected to the base electrode of the transistor 2 in the present case. This avoids the slight negative signal feedback caused essentially by the resistor 13 in FIG. 2, for which an additional decoupling capacitor would otherwise be required for the base electrode of the transistor 2.

In Fig. 4 a modification of Fig. 3 is shown in which the transistors 1 and 2 in per se are connected in series for the direct current supply, as is known. The resistor 9 is included by the internal collector resistance of the resistor 16 with decoupling capacitor 15 stabilized transistor 1 is formed.

Fig. 5 shows another modification of Fig. 3, in which two transistors 1 and 2 'from opposite to -8o set conductivity type can be used. For this purpose the resistor 9 'is included to connect the other pole of the supply source 12, and the secondary windings 7 'and 8' must reversed to achieve the required reduction in DC bias.

In the illustrated 'circuit arrangements the secondary windings 7, 8 or 7 ', 8' are always combined into one winding with a tap. Of course, however, the winding 8 or 8 'and the resistor 9 or 9' could if desired be swapped in the emitter series, which make the transformer 3 a bit more complicated would. Of course, the cascade shown can also have a third correspondingly stabilized one and transistor coupled via a transformer or the cascade, if applicable be expanded even further.

Claims (6)

PATENT CLAIMS: i. Amplifier with two transistors, in which the collector circuit of the first transistor via a matching transformer with the emitter circuit of the second in basic connection lying transistor is coupled, characterized in that the transformer with two Secondary windings are provided, together with a stabilization resistor are flowed through in series by the direct current of the second transistor, while only one of these secondary windings., expediently the winding with the lowest number of turns, Via a coupling capacitor between the emitter or base electrode of the second transistor for the signal voltage is effective, so that direct current disconnection of the transformer prevented and at the same time the operating point of the second transistor iao stabilized isit. 2. Amplifier according to claim i, characterized characterized in that the two secondary windings form a winding with a tap are united and the tap via the ias Coupling capacitor with one of the two Input electrodes of the second transistor is connected. 3. Amplifier according to claim 2 ,. in which the tapping of the secondary winding via the Coupling capacitor is connected to the emitter electrode of the second transistor, thereby characterized in that the stabilization resistor (9) is located directly between the secondary winding and emitter electrode is connected (Fig. 1,2). 4. The amplifier of claim 2, wherein the tapping of the secondary winding via the Coupling capacitor is connected to the base electrode of the second transistor, thereby characterized in that the stabilization resistor (9 ') is located directly between the secondary winding and the supply source (12) of the transistors is connected (Fig. 3). 5. Amplifier according to one of claims 1 to 4, characterized in that the stabilizing resistor wholly or largely from the inherent resistance of the secondary part winding with the largest number of turns. 6. Amplifier according to one of claims 1 to 4, characterized in that primary and Secondary windings of the matching transformer for the direct current supply are connected through and the stabilization resistance for the second transistor by the internal collector resistance of the first transistor, the operating point of which is stabilized by itself, is formed (Fig. 4). Considered publications:
German patent specification No. 684 800. 1 sheet of drawings Θ 609 620004. 9. » (709 861/2 * 1.58)