US2284064A - Amplifier - Google Patents

Description

May 26,1942. A. R. MORGAN I AMPLIFIER Filed Jan 25, 1941 Wi l:-

Patented May 26, 1942 zgsiosi AMPIJFIEE Adolph R. Morgan; Merchantyille, N. J., assignor to Radio Corporation of America, a'corporation of Delaware Application January 25, 19 41,?Serial No. 375,893

9 Claims. (01. 119-171) This invention relates to an amplifier inwhich a voltage from a single source is amplified and converted intoa two-phase or push-pull source.

. More particularly the' invention relates to a direct current amplifier for amplifying and converting potentials from a single-endedscircuit into pacitors are used to prevent undesired bias potentialsfrom being applied to the input circuits of. the push-pull amplifier which follows the first amplifier. If these capacitors are eliminated, the bias potentials applied to the input of the push-; pull amplifier would unbalance, and perhaps make inoperative, that amplifier. The unbalanced amplifier would not perform the desired function. I

One of the principal objects of the present invention is to provide means whereby an amplifier and associated circuit may be used to amplify and convert a single-phase current into an amplified current of two phases. Another object is to provide means for the amplification of a direct current whereby currents of equal magnitude and opposite sense, with respect to each other, may be obtained. A further object'is to provide means in a direct current amplifier whereby currents from' a .siugle-ended" circuit may be amplified and converted into currents suitable for application to apush-pull amplifier.

The invention will be described by referring to the accompanying drawing in which Figure 1 is a schematic circuit diagram of one embodiment of the invention; Figure 2 is a schematic circuit diagram of an embodiment of the invention in which a single-ended circuit maybe connected to a push-pull-amplifier provided with an alter- 'nating current output circuit; and Figure 31s a graph illustrating the operation of the circuit.

Referring to Fig. 1, input terminals 1 and 3 are connected respectively to thegrid; of .an amplifier 5 arid to the groundejdmid-point 'I of a pairof B batteries EBI and E32. The anode of of the amplifier 5 is-connected through a resistor R2 to the negative terminal of the battery EBZ.

The remaining. battery terminals are connected to ground as shown. A potentiometer comprising resistors R3 and R4 is connected between the cathode of the amplifier and the positive terminal of the battery EBI. A second potentiometer comprising resistors R5 and R6 is connected between the anode of the amplifier and the negative terminal of the battery E32. The movable contacts 9 andII', respectively, of the potentiometers' are connected to output terminals I3, I5.- The output voltages EM and EH) appear between the output terminals I3 and I5, and .the intermediate battery terminal or ground;

The preferred practical use of the device is an adjustment producing a truly push-pull output,

namely, one in which the amplified signals are equal in magnitude and opposite in phase. In this practical use of the device, the batteries EBI and E132 are preferably of equal potential. The resistors RI. and R2 are preferably of equal -value and the sum of these resistors RI and R2 is chosen to representa suitable loading forthe amplifier 5. The sum of the resistances R3 and RI preferably equals the sum of the resistances .R5 and R6. Furthermore, the sum of theresistors R3 and R4 is preferably of the order of 10 times RI. The final practical requirement isthat the ratio of R3 to,R4 is equal to the ratio of R6. to R5 as will hereinafter be explained.

Thooperation of the circuit is as follows: The currentthrough resistors RI and R2 is the same.

Therefore; the voltage drop across RI will equalthe voltage drop across R2, since RI equals R2. If a-positive .potentia1 is applied to the terminal I, withrespect to terminal 3, the current through "the resistors RIland R2 will be increased over the value which'ismaintained in the absence of an input signal. 'The increased current will be accompanied by increased voltage drops-"across the resistors RI and R2. It follows that the volt the amplifier 5 is connected through a resistor-RI agesbetween the anode and ground and the voltages between the cathodea'nd ground willchange ina push-pull manner as will the voltages E211 and E217. B'y suitably adjusting the potentiometers the ratio of R3 to R4 and R6 to R5 may bedetermined so that the voltage changes in the output of the amplifier will be equal and opposite with respect to each other. Furthermore, the

' quie sc ent or no signal output voltages for this adjustment, will be equal in magnitude and opposite in" polarity, It follows thatv the quiescent voltages can be adju'stedto any value between FBI (or E132) and the diiference in voltage bein supply potential.

tween E3! (or E32) and the drop across R or (R2).

By way of example, reference is made to Fi 3 with a zero input signal El. The potentiometers may be adjusted so that nan. R4 R5 and EM will equal E217, and the steady voltage equals zero. Thus adjusted. thesloping lines in the graph represent the corresponding changes in output current as the input potential is made more negative or more positive.

It is not intended that the adjustment of this circuit be limited to truly push-pull operation. Any number of combinations of Eta and E2b can be obtained dependent on the adjustment of for the amplifier is not to be limited to batteriesand that the power may be applied from a. suitable generator or rectifier and filter. In con--.

nection with power sources other than batteries.- itshould be evident to those skilled in the art that this circuit (particularly the truly push-pull adjustment) is relatively insensitive to changes Furthermore, any type of push-pull output amplifier may be used, as'ior example, the a-c amplifier of Fig. 2 in which the input potentials E211, EZb are applied to the push-pull amplifiers l1 and I9, respectively. The output circuits of the push-pull amplifiers include a conventional output transformer 2|.

I claim as my invention:

1. An amplifier for ampliiying and converting a single steady current into currents of opposing characteristics including an amplifier having grid, anode, and cathode electrodes, 8. power source having end terminals and an intermediate -terminal, resistors connectingrespectively said and anode electrodes; a power source having a.

positive terminal, a'negative terminal, and an intermediate terminal; a pair of resistors connecting respectively said anode to said positive terminal and said cathode to said negative terminal; means for applying between said grid and said intermediate terminal the direct current to be converted, a pair of potentiometers connected respectively between said anode and said negative terminal and between said cathode and said positive terminal; and means connected respectively to each of said potentiometers for deriving 7 between said respective connecting means and said intermediate terminal said direct currents of.

opposing characteristics.

3. An amplifier forconverting a direct current into two equal direct currents of opposing characteristics including an amplifier having grid, cathode, and anode electrodes; a power source. having a positive terminal, a negative terminal, and an intermediate terminal; a pair of resistors of equal value connecting respectively said'anode to said positive terminal and said cathode to said negative terminal; means for applying between said grid and said intermediate terminal the direct current to be converted, a pair of potentiometers connected respectively between said anode and said negative terminal and between said cathode and said positive terminal; and means connected respectively to each of said potentiometers for deriving between said respective connecting means and said intermediate terminal said direct currents of opposing characteristics.

4. An amplifier for converting a direct current into two equal direct currents of opposing characteristics including an amplifier having grid, cathode, and anode electrodes; a power source having a positive terminal, a negative terminal, and an intermediate terminal; a pair of resistors of equal value connecting respectively said anode to said positive terminal and said cathode to said negative terminal; means for applying between said grid and said intermediate terminal the direct current to be converted, a pair of potentiometersconnected respectively between said anode and said negative terminal and between said cathode and said positive terminal; said potentiometers each having of the order of ten times means connected respectively to each of said potentiometers for deriving between said respecsaid anode and said negative terminal and be tween said cathode and 'said positive terminal,

tive connecting means and said intermediate terminal said direct currents of opposing characteristics. I 5. An amplifier for converting a single variable current into two currents which vary in opposite sense including an amplifier having grid, cathode and anode electrodes, a power source having positive and negative terminals and a center tap, a pair of resistors of similar value connected respectively between said positive terminal and said anode and between. said negative terminal and said cathode, means for applying said single phase current to said grid and center tap,

output terminals for obtaining said currents be- 1 tween said center tap and voltage points intermediate said anode and said negative terminal and said cathode and said positive terminal, and means for adjusting said output terminals so that a predetermined current is obtained between each of said output terminals :and said center tap.

6. An amplifier for converting a single variablecurrent into two currents which vary in opposite sense including an, amplifier having grid, 'cath- I ode and anode electrodes, 9. power source having positive and negative terminals and a center tap,

a pair of resistors of similar value connected re-' spectively between said positive terminal and said anode and between said negative terminal and said cathode, means for. applying said single phase current to said grid and center tap, a pair of potentiometers connected respectively between and means ior adjusting said potentiometers so that said currents are obtained between the adjustable contact of each of said potentiometers and said center tap. V 7. An amplifier for converting a single variable current into two currentswhich vary in opposite sense including an amplifier having grid, cathode and anode electrodes, a power source having positive and negative terminals and a center tap, a pair of resistors of similar value connected respectively between said positive terminal ,and said anode and between said negative terminal and said cathode, means for applying said single phase current to said grid and center tap, a pair of potentiometers connected respectively between said' anode and said negative terminal and between said'cathode and said positive terminal, and means for adjusting said potentiometers so that zero quiescent voltage with respect to said center tap is obtained between the adjustable contact of each of said potentiometers and said center tap and said two variable currents are obtained between said contacts and said center tap.

8. The combination of end and intermediate power'supply terminals, a pair of direct current circuits including reversely arranged impedance sections connected-in parallel between said end terminals, means for similarly varying the current through one pair of the opposite end sections of said circuits, and means connected between said intermediate terminal and the other opposite end sections of said circuits for deriving'voltages displaced in phase from one another. i

, 9. The combination of end and intermediate power supply terminals, a pair of direct current circuits including reversely arranged impedance sections connected in parallel between said end terminals, an electron discharge device provided with an input circuit including said intermediate terminal and with an output circuit including one pair of they opposite end sections of said circuits, and means connected between said intermediate terminal and the other pair of the opposite end sections of said circuits for derivingvoltages displaced in phase. ADOLPH R. MORGAN.

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