Abstract:
A power amplifier system measures the amount of power supplied to the voltage supply pins of an operational amplifier, and supplies a proportional amount thereof to drive power amplifiers. A comprehensive system analyzer is used to protect the circuit and the load against power excesses.

Description:
This is a continuation of Ser. No. 07/131,898, filed on 12/11/89 and now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to power amplifiers, and more particularly to operational amplifier driven power amplifiers. 
     2. General Background 
     Operational amplifiers, (OP AMPS), are used today as power amplifier drivers. Typically, the output of the op amp is used to drive the power amplifier. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention uses the voltage supply pins of an operational amplifier to drive power amplifiers. A comprehensive system analyzer is used to protect the circuit and the load against power excesses and reveals the problems on an indicator means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1 is a block diagram of the preferred embodiment of the present invention; 
     FIG. 2 is a mixed circuit/block diagram of the preferred embodiment of the present invention; 
     FIG. 3 shows blocks C-a and D-a of a second embodiment of the present invention; 
     FIG. 4 shows blocks C-b and D-b of the second embodiment of the present invention; 
     FIG. 5 shows an alternative embodiment of block F; 
     FIG. 6 is a circuit/block diagram of block G; and 
     FIG. 7 is a flow chart of block G. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a block diagram of the present invention, power amplifier 100. Block A is a switch to connect the non-inverting input pin 3 of operational amplifier (OP AMP) B to signal source 10 or non-signal source 11 (ground). It is controlled by block G, as will be described further. 
     OP AMP B has an inverting input, non-inverting input, and output and uses two power supplies (+Vee and -Vee). It has a non-inverting input pin 3 to, an inverting input pin 2, a first voltage supply pin 4, an output pin 6, and a second voltage supply pin 7. 
     Blocks C-a and C-b supply current and voltage to OP AMP B, and keep the voltage within the maximum magnitudes of power supply voltages (+Vee, +Vee). Blocks C-a and C-b drive a constant ratio of current or voltage by supplying current of OP AMP B to blocks D-a and D-b. Blocks C-a and C-b may be termed &#34;measuring and driving means&#34; or &#34;voltage level shifter circuit means. &#34; 
     Blocks D-a and D-b are power amplifiers and serve to supply appreciable power to load Rd. 
     Block E is a feedback network between the output of OP AMP B and load Rd. 
     Block F is a feedback network between the inverting input of OP AMP B and load Rd. 
     Block G is a system analyzer to controls, Block A and Block H, determined by +Vcc, -Vcc, load Rd and current to load Rd. The flow chart for Block G is shown in FIG. 7. 
     Block H contains system indicators controlled by Block G. 
     Load Rd may comprise, for example, a speaker. 
     Referring now to FIG. 2, where some circuitry is shown, Block A contains a switch to connect the non-inverting input pin 3 of OP AMP B to either signal source 10 or ground 11. 
     Only the general schematic of the output section of OP AMP B is shown in FIG. 2. The general input stage of OP AMP B is a differential amplifier circuit. OP AMP B may comprise, for example, an LF351 or a TL071. 
     Load resistors R-1 and R-101 generate the necessary bias and drive voltages that blocks D-a and D-b require. Voltage +VDD will be determined by i2 and R1 as follows: 
     
         ______________________________________i2 = C1 × i1 (where C1 is a constant)Vcc = VDD + i2 × R1Vcc - VDD = i2 × R1 = C1 × i1 × R1Vz = VDD - Vee.______________________________________ 
    
     In FIG. 2, Block D-a comprises a P-channel MOSFET, and Block D-b comprises an N-channel MOSFET. 
     In FIG. 2, resistors R3 and R4 are shown in Block E, which is a voltage feedback circuit. Block E creates additional gain which improves the band-width, slew rate, reduces distortion of the amplifier, and improves the gain-band-width product. Compensation could be added in Block E for phase characteristics. 
     Block F is a negative feedback circuit which can consist simply of resistors R7, and R8, as shown in FIGURE 2. This negative feedback circuit controls the gain (vout/vin). Compensation could be added for overall gain and phase characteristics, such as shown in FIG. 5 (capacitors C-7 and C-8). 
     FIGS. 3 and 4 show blocks C-a, C-b, D-a, and D-b of a second embodiment of the present invention. 
     Transistor Q2 may comprise a PNP bipolar transistor or a Darlington transistor. Transistor Q202 may comprise an NPN bipolar transistor or a Darlington transistor. In FIGS. 3 and 4, R1 and R101 are drivers for Blocks D-a and D-b. R2 and R102 supply voltage to the base of transistors Q1 and Q101. Voltage Vz=Vee+0.7 V. The relationships between il and i2 and Vcc and VDD are the same as with Blocks C-a and C-b shown in FIG. 2. 
     FIG. 6 is a circuit/block diagram of Block G. In FIG. 6, Blocks G-a, G-b, G-c, and G-d are shown, along with logic inverters 20, and logic AND gate 21. Blocks G-a, G-b, G-c, and G-d comprise comparative circuits. A flow chart showing the actions of these blocks is shown in FIGURE 7. The legend for FIG. 7 is set forth below. 
     
         ______________________________________LEGEND FOR FIG. 7+Vcc:  POSITIVE POWER SUPPLY VOLTAGE-Vcc:  NEGATIVE POWER SUPPLY VOLTAGEVpmin: MINIMUM VOLTAGE OF +Vcc TO OPERATE  THE CIRCUITS PROPERLYVpmax: MAXIMUM VOLTAGE OF +Vcc TO OPERATE  THE CIRCUITS PROPERLYVnmin: MINIMUM VOLTAGE OF -Vcc TO OPERATE  THE CIRCUITS PROPERLYVnmax: MAXIMUM VOLTAGE OF -Vcc TO OPERATE  THE CIRCUITS PROPERLYRdmin: MINIMUM LOAD IMPEDANCE TO OPERATE  THE CIRCUITS PROPERLYIrd:   CURRENT TO A LOAD RdIrdmax:  MAXIMUM CURRENT OF Ird TO OPERATE  THE CIRCUITS PROPERLYDESCRIPTION OF ACTIONS:ACTION A: CONNECT INPUT PIN 3 OF OP AMP-B TO     SIGNAL SOURCE 10ACTION B: CONNECT INPUT PIN 3 OF OP AMP-B TO     NON-SIGNAL SOURCE 11ACTION C: INDICATE &#34;+Vcc FAIL&#34; THROUGH     BLOCK HACTION D: INDICATE &#34;-Vcc FAIL&#34; THROUGH     BLOCK HACTION E: INDICATE &#34;LOAD FAIL&#34; THROUGH     BLOCK HACTION F: INDICATE &#34;TOO HIGH LOAD     CURRENT&#34; THROUGH BLOCK HACTION K: INDICATE &#34;ALL RIGHT&#34; THROUGH     BLOCK H______________________________________ 
    
     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.