DE1772626B2 - SWITCH FOR ELECTRONIC MUSICAL INSTRUMENTS - Google Patents

Description

The invention relates to a switch for electronic musical instruments with a transistor, whose base is connected to a pulse generator, in whose emitter branch a key switch and a hold circuit and an output signal can be taken from its collector.

A switch of this ArI is in the United States patent 3 141919. Other electronic switches for operating musical instruments as a replacement for the previously common mechanical switches are also from the USA. patents 2,486,208 and 3,247,306 as well as the German Auslegeschrift 1 181 030 known. The main flaw of all these known switches is that even when the key switch is in the OFF position a small part of the applied pulse signal via parasitic capacitances, such as those for example are present between the collector and the base of a transistor, flow as the supplied Pulse signals have a high proportion of harmonic components with a very high frequency. These leakage currents, which have so far been practically ignored and certainly not combated have, ultimately lead to a sound generation even if the individual key switches associated components of the electronic musical instrument are not recorded at all should. This naturally results in a disruptive falsification of the playing of the electronic musical instrument desired sound quality and can even result in the electronic musical instrument Emits sounds, ohi.e that it is played at all.

The invention is therefore based on the object of designing a switch of the type mentioned at the outset in such a way that that when the key switch is in the OFF position regardless of the frequency composition of the supplied pulse signals, no current can flow through the entire switch.

This object is achieved in that between the pulse generator and the A diode is inserted into the base of the transistor.

In the switch designed according to the invention, the supply of the pulse signals to the transistor base takes place via the diode, which is biased in the reverse direction when the key switch is in the OFF position, so that no harmonic components of the pulse signals are transmitted because the diode has a high impedance at this time In addition to the total avoidance of undesired leakage currents which can be achieved in this way when the switch is switched off, the invention offers the further advantage that transistors with an emitter-base-pn junction with a relatively low breakdown voltage can be used for the construction of the switch, since the pulse signals of the transistor base are not un -

are fed indirectly, but get there via the diode and this has a very high impedance while the key switch is in its OFF position.

For the further explanation of the invention

now referring to the drawing; in this shows

F i g. 1 is a circuit diagram for a conventional switch arrangement for electronic musical instruments,
F i g. 2 a circuit diagram for a first embodiment

ao the form of a formwork instruction for electronic musical instruments and

F i g. 3 is a circuit diagram for a second embodiment of a switch arrangement according to the invention for electronic musical instruments.

1 shows a conventional switch arrangement of the previous type, the reference number 1 denoting a tone generator, the reference number 2 denoting a transistor, the reference numbers 5 and 6 denoting bias resistors, the reference number 7 denoting a load resistance and the reference number 8 denoting an emitter resistance. In addition, a circuit 4 is provided for influencing the decay behavior of the output signal, which circuit consists of an opposing circuit 9 and a capacitor 10. + K ₁ denotes a voltage source for the operation of the transistor 2 and V, _{} denotes} a voltage source which supplies the emitter of the transistor 2 with a reverse bias. Reference numeral 3 denotes a key switch which can be closed by depressing the key. Reference number 11 denotes a resistor and reference number 12 denotes an output terminal. In addition, there is usually a resistor between the tone generator 1 and the node 13, which, however, is shown in FIG. 1 is not shown.

During operation, the emitter-base junction of the transistor 2 is initially strongly biased in the reverse direction by the voltage source -> ■ V., the key switch 3 being in its open position

so position is located.

In this way, the transistor 2 remains non-conductive for this input signal voltage even if it is supplied with an input signal voltage C by the tone generator 1, so that this input signal voltage £ "is essentially not passed on to the output source 12. However, at the output terminal 12 This leakage signal probably arises from the fact that the input signal voltage E _s reaches the output terminal 12 via the junction capacitor 14 between the collector and the base of the transistor 2.

If the key switch 3 is then closed, the emitter-base junction of the transistor 2 is biased slightly in the forward direction, and the transistor 2 can take over its normal switch function and thus forward the input signal voltage E _s to the output terminal 12.

With the switch arrangement described above, the operation of the circuit 24 for envelope

is thus the collector-emitter path forming the transit and to bias the diode 32 in the back-

sistor 2 by opening or closing the key downward direction via the resistor 25 and a

switch 3 non-conductive or conductive and is capable of further resistance 28 when the key switch is open

with respect to the output signal of the tone generator 1 5 ter 23 denotes.

in the manner described above as a switch ^ u we- Next, the mode of operation of the above-mentioned

ken. Such a conventional switch arrangement has a written switch arrangement or the hold circuit

however, when it was built into an electronic music system. Initially, the diode 32 is

instrumeni, such as B. an electronic organ an open key switch 23 via the resistors 25

Has a large number of keys, the disadvantage that with io and 28 from the voltage source + K ₄ , whose posi-

high probability then a sound signal tive potential is selected greater than the peak value

from the tone generator 1 is audible, if none of the input signal voltage, in reverse direction

of the keys is printed, because the open-close-clamps. The capacitor 29 is also up to about

Ratio (ie the ratio S _ci / S _uus between the voltage f K ₄ charged, and so is that

the voltage level S _ti "of the output signal, the 15 potential at the node 35 essentially

with key switch 3 closed at c'er output - equals + K ₄ . The potential + V ₃ is equal to the Po-

kleüimc 12 occurs, selected at the voltage level S ₁₁₁₁₁ , potential -f K ₄ or less. That means that

of the leakage signal with the key switch 3 open on which the transistor 22 is biased so that it is in the remaining

Au ^ '- iingsklcmme 12) is too small. River basin or be; low current in its aftermath

In addition, the node 13 from which the barscliafl works and therefore its reinforcement in the

Tiüvenerator 1 constantly a signal voltage E, essentially to zero. To those with the base of the

led, since the emitter-base breakdown transistor 22 connected node <34 reached

voltage of the transistor 2 is not very large, a signal that is due to the high impedance of the in

/ u; n breakthrough of the emitter barrier leads to realignment of biased diode 32

knfii. 25 is attenuated, since the impedance between the node

With the invention, these disadvantages of the point 34 and the ground potential or the reference

iiWhile switch arrangement can be eliminated. At potential is less than the reverse impedance of

An embodiment of the invention is in the diode 32. The signal attenuated in this way can be applied to this

The main branch of the transistor has an asymmetrical design, on the one hand, no breakthrough in the emitter

ekment, such as B. a diode, inserted, wherein mit- 30 cause a barrier layer of the transistor 22, and

te! are provided that are synchronous with the open on the other hand; mders than with the usual circuit

oil ¹ '. ■; ■ closed state of a holder, as is essentially not the case with the output terminal 33

for example a key switch, the diode one can be forwarded.

Bias in the reverse direction or in front If the key switch 23 is then upward direction respectively. In this way, the 35 is closed, so the potential on the node diode then, when the key switch is at its point 35 within a short period of time, from otlen state is a high impedance, the product of the capacitance of the capacitor 29 whereby an applied to the anode of the diode and the value of the opposite resistor 28 very much Signal only strongly weakened depends on the base of the tran- small contradiction 30, like the earth transistor got. Such a signal weakening leads to 40 potential. At that moment the diode becomes 32 then forward biased to an increase in open-close and work ratio and a reduction in the melting point of the transistor 22 gets into its active nuisances in connection with emitter junction rich, so that the transistor 22 with a predetermined breakdown. NEN amplification begins to work as an amplifier

In prop. Fig. 2 is such a first embodiment 45 and the output of the tone generator 21 to that

of the invention, reference number going output terminal 33. Since the diode 32 is like

21 a tone generator, which is a rectangular shape mentioned above is biased in the forward direction,

Output signal generated, the reference number 32 with it does not stand in any such signal transmission

the tone generator 21 connected pn junction way opposite.

diode, the reference number 22 an npn transistor, des- 50 Next, the key switch 23 is again in sen base the output signal of the tone generator 21 transferred to its open state. At this time the diode 32 is supplied, and the reference point returns the potential at the node 35 number 27 denote a load resistance, which does not instantly return to its initial value of in one end with a positive voltage source + K ₃ essentially + K ₄ . Rather, this and its other end takes on the one hand the collector potential at the node 35 only gradually gate of the transistor 22 and on the other hand is connected to one of the charging characteristics of the Kon output terminal 33. The reference number deiv i; ors 29, which essentially derives from the time 24, designates a circuit for generating a constant RC from the value R of the resistor 28 envelope curve, which is a function of a resistor 28 and a capacitance C of the capacitor 29. Capacitor 29 exists and is connected to the emitter of 60. As soon as the potential at the node 35 closes transistor 22 via an emitter resistor 31, the value + K ₄ is reached again. The reference number 23 denotes a key switch connected to both the diode 32 and the transistor 22 and the emitter of the transistor 22 via resistors 30, which are in their original bias state, and 31 for control and thus a forwarding of the output signal of the bias states for the transistor 22 and 65 of the tone generator 21 to the output terminal 33 for the diode 32. The reference numerals 25 and 26 prevent.

draw bias resistors for the Tran- The transistor 22 does not get to the immediately

sistor 22. and with ^J -K ₁ is a voltage source for opening the key switch 23 in its original

5 ⁴ 6

normal preload condition. That means that yourself

the bias condition for transistor 22 in Table 1

Opening the key switch 23 gradually from that.

State that it has when switch 23 is closed - the peak value of the rectangular
is shaped. changed to the steady state when the output signal of the tone switch 23 is open, so that 10 V at the output generator 21

Terminal 33 still has diode 32 IS1473 even when switch 23 is open

an output signal transistor 22 npn silicon for a predefinable period of time

is available. The amplitude of the transistor 2 SC 458 in this way

sustained output signal essentially takes + F 12 V voltage source

borrowed exponentially with the time constant of the for the snapshot source + F ³ 10 V

Envelope formation of the decisive element 24, so ^r ,? -> = ⁴

that there is a so-called .Viderstand 25 20 kΩ in the output signal

Il envelope forms. Fine such an envelope curve in the resistor 26 8OkΩ

The signal is necessary for the generation of a natural sound. 15 Resistance 27 400 Ω

tot for every electronic musical instrument of resistance 28 50 kQ

great importance, which is why you should, as above, resistance 30 63 Ω

thinks it is a combination of a key switch "

with an electronic amplifier element and resistor 31 0.1 Ul

a circuit for the envelope curve formation instead of ao capacitor 29 50 i.F

operated by a key switch alone.

The cause of the increase in the open-closed

The ratio can be shown as follows: In a circuit according to FIG. 2, the capacitance between the electrodes of the characteristic diode 32 compiled in Table 1 above and the impedance between the node sizes is open -The closed relationship at point 34 and the grounding point act in the blocked-a signal frequency of 1 kHz in a range of th state of the diode as a kind of high-pass filter, SO to 90 dB. The signal level under reference is that the lower harmonics would take corresponding to the peak-to-peak value of the signal voltage components in the rectangular output signal of the measured. From this measurement, tone generator 22 can be filtered away at the same time, while the 30 ¹ ^ e advantageous effect of the circuit according to FIG. 2 higher harmonics "through this filter - compared to the circuit according to FIG With this circuit, an open harmonic component of the tone generator signal closed ratio of about 50 dB can at best be achieved, which is then fed into a further high-pass filter The embodiment of a switch assembly transistor 22 according to the invention and the impedance between the cutout differs from the embodiment shown again in FIG executed electronic switch In this way appears at the output terminal Use fin det. In their basic working 33 only a small, extremely high harmo- +0 wise, the two switch arrangements are that "existing portion of the output signal of the but essentially the same.

Tone generator 21. One such from "high harmo- In FIG. 3, the collector of a transistor 42

However, the existing signal has itself grounded via a load resistor 47 and is as

when there is a tone generator 41 between earth and signal source in subsequent switching stages

is strengthened, none for Betnebe a loudspeaker 45 one at a node 54 with the base of the

adequate performance. In addition, the diode 52 connected to the human transistor 42 is connected,

borrowed ear even "when the speaker is through to the emitter of transistor 42 through a

such a signal should be set in motion, a curve forming a curve for emitter resistor 51

these higher harmonic components of the primary circuit 44 from a contradiction 48 and a

not sensitive to the initial sound signal. 50 capacitor 49 connected. Between a nodal

As mentioned above, there are essentially no lower harmonic switches 43 at the node 55 and an output terminal of a key point 34. a potential _{source F 5} , a resistor and even this very weak audible frequency connector 50 is inserted. A bias resistor 45 is located between the nodes 54 and parts as they continue to pass through the 55 55. The upper collector boundary layer capacitance is further attenuated. Transmission of the output signal of the tone generator 41 As a result, the voltage level 5 _o , _is to e ^; The output terminal 53 is controlled by the leakage switch 43 that appears on the output terminal 33. With such a switch signal very low, and the oven-closed arrangement can not only increase the desired holding container (S _t 1, "S _off ) . This is one of the goals to create an effect, but one also arrives at one of the invention. satisfactory open-close ratio and

If one considers the embodiment of the invention dealt with in the description above, the risk of an emitter-Spcrrschichi breakdown can be significantly reduced,
speaking F i g. 2 of the drawing, it shows in a practically executed game for one that a satisfactory operation of such a circuit according to FIG. 3 could be an arrangement is possible. if the individual satisfactory working methods are measured using the table 1 shown in the parameters and stresses in the parameters compiled in Table 2 below. achieve.

7 8

The embodiments described above for

Table 2 according to the invention contain switch arrangements as

Amplifier elements bipolar transistors, namely

Peak value of the rectangular npn transistor, and as an unbalanced construction output signal des lon- 5 element diodes with a single pn junction,

generator 41 10 V, however, it is obvious to those skilled in the art that

Diode 52 IS1473 you can use unipolar transistors instead, like

Transistor 42 npn silicon - e.g. surface field effect transistors or others

Transistor 2 SC 458 can use equivalent semiconductor components.

Resistance 45 5 kQ ok In addition, there is a Tongenera resistor in the examples 47 200 Ω tor with a square output signal as a signal resistor 48 40 kQ source described and illustrated, but can take place

Resistance 50 50 Ω which also easily has a signal source

Capacitor 49 50 uF using a sinusoidal output signal

Find voltage source c -F ₅ 12 V 15.

1 sheet of drawings

Claims (1)

Claim: Switch for electronic musical instruments with a transistor whose base is connected to a pulse generator, in whose emitter branch a key switch and a hold circuit are located and at whose collector an output signal can be taken off, characterized in that between the pulse generator (21; 41) and the base of the A diode (32; 52) is inserted into the transistor (22; 42) .