Circuit configuration for generating a d-c output voltage independent of fluctuations of a d-c supply voltage

Circuit for generating a d-c output voltage being independent of fluctuations of a d-c supply voltage, including a reference voltage circuit connected to a d-c supply voltage source, the reference voltage circuit including a series circuit of a constant-current source and a potenatial shift branch, an inverting amplifier being connected to and addressed by the reference voltage circuit, the inverting amplifier having an output circuit including a combination of a plurality of first resistors and at least one first transistor determining the gain of the inverting amplifier, an output driver supplying the d-c output voltage, the output driver being connected to and addressed by the inverting amplifier and the output driver having an output circuit being connected to the potential shift branch of the reference voltage circuit for driving the potential shift branch, the output driver including an emitter follower stage having an output circuit with a second transistor and a second resistor, a voltage stabilizing circuit having a tap carrying a prestabilized voltage and the voltage stabilizing circuit being connected to the d-c supply voltage source, a third resistor connected between the tap and the at least one first transistor in the output circuit of the inverting amplifier, and a fourth resistor connected between the tap and the second transistor in the emitter follower output circuit of the output driver, the first, second, third and fourth resistors having the same resistance value.

The invention relates to a circuit arrangement for generating a d-c output 
voltage which is independent of fluctuations of a d-c supply voltage, 
especially for addressing current-source transistors for feeding 
integrated circuits, including a reference voltage circuit connected to 
the d-c supply voltage in the form of a series circuit of a 
constant-current source and a potential shift branch, an inverting 
amplifier being addressed by the reference voltage circuit and having an 
output circuit with a combination of resistors and at least one transistor 
which determines its gain, and an output driver which is addressed by the 
inverting amplifier, which supplies the d-c output voltage, and which has 
an emitter follower stage and a transistor connected in the output circuit 
thereof, the output driver addressing the potential shift circuit in the 
reference voltage circuit. 
A circuit configuration of the type mentioned above is known from German 
Published, Non-Prosecuted Application DE-OS 28 49 153. With such a circuit 
arrangement, d-c output voltages can be generated which are independent of 
a d-c supply voltage, where load variations have practically no influence 
on the d-c output voltage. However, the supply voltage and the temperature 
range for which independence of the d-c output voltage with respect to the 
d-c supply voltage applies, is particularly insufficient in many cases. In 
addition, the current gain of transistors used in the circuit arrangement 
cannot be compensated in the known circuit arrangement. 
It is accordingly an object of the invention to provide a circuit 
configuration for generating a d-c output voltage which is independent of 
fluctuations of a d-c supply voltage, which overcomes the 
hereinafore-mentioned disadvantages of the heretofore-known devices of 
this general type, and in which the d-c output voltage that is generated 
is constant over a wide range of supply voltage, temperature, component 
parameters and particularly current gain of bipolar transistors. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a circuit for generating a d-c output 
voltage being independent of fluctuations of a d-c supply voltage, 
particularly for addressing current-source transistors for feeding 
integrable circuits, comprising a reference voltage circuit connected to a 
d-c supply voltage source, the reference voltage circuit including a 
series circuit of a constant-current source and a potential shift branch, 
an inverting amplifier being connected to and addressed by the reference 
voltage circuit, the inverting amplifier having an output circuit 
including a combination of a plurality of first resistors and at least one 
first transistor determining the gain of the inverting amplifier, an 
output driver supplying the d-c output voltage, the output driver being 
connected to and addressed by the inverting amplifier and the output 
driver having an output circuit being connected to the potential shift 
branch of the reference voltage circuit for driving the potential shift 
branch, the output driver including an emitter follower stage having an 
output circuit with a second transistor and a second resistor, a voltage 
stabilizing circuit having a tap carrying a prestabilized voltage and the 
voltage stabilizing circuit being connected to the d-c supply voltage 
source, a third resistor connected between the tap and the at least one 
first transistor in the output circuit of the inverting amplifier, and a 
fourth resistor connected between the tap and the second transistor in the 
emitter follower output circuit of the output driver, the first, second, 
third and fourth resistors having the same resistance value. 
The circuit configuration defined above has the advantage of substantially 
increasing the range of output voltages by prestabilization; reducing the 
current drain for large d-c output voltages; substantially reducing the 
influence of the d-c supply voltage on the d-c output voltage; and keeping 
the influence of the current gain of the transistors used in the circuit 
arrangement on the d-c output voltage negligibly small. 
In accordance with another feature of the invention, there is provided a 
fifth resistor being connected between the output circuit of the output 
driver and the potential shift branch of the reference voltage circuit. 
In accordance with a further feature of the invention, the second resistor 
of the emitter follower stage of the output driver is a working resistor 
being equal in resistance value to the fifth coupling resistor. 
In accordance with an added feature of the invention, the resistance value 
of the fifth coupling resistor is equal to n-times the resistance value of 
the second working resistor of the emitter follower stage of the output 
driver. 
In accordance with an additional feature of the invention, the 
constant-current source includes a third transistor, and the output 
circuit of the output driver includes a fourth transistor forming a 
current mirror with the third transistor. 
In accordance with a concomitant feature of the invention, the potential 
shift branch includes a reference diode. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
circuit configuration for generating a d-c output voltage independent of 
fluctuations of a d-c supply voltage, it is nevertheless not intended to 
be limited to the details shown, since various modifications and 
structural changes may be made therein without departing from the spirit 
of the invention and within the scope and range of equivalents of the 
claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying single FIGURE of the drawing 
which is a diagrammatic and schematic circuit diagram of an embodiment of 
the circuit according to the invention.

A reference voltage circuit 11 is connected to the d-c supply voltage 
U.sub.O. The reference voltage circuit 11 is formed of a voltage divider 
which is formed by a constant-current source in the form of a transistor 
T.sub.12 (optionally with an emitter resistor) and a potential shift 
branch in the form of the series circuit of a transistor T.sub.11 and a 
reference diode D.sub.11. 
The reference voltage circuit 11 addresses an inverting amplifier 12. The 
inverting amplifier 12 has a gain -1, and includes a transistor T.sub.22, 
a collector resistor R.sub.22 and an emitter resistor R.sub.23. A further 
resistor R.sub.21 is inserted into the collector circuit of the transistor 
T.sub.22. 
The inverting amplifier 12 controls an output driver 13 with a transistor 
T.sub.32 connected as an emitter follower. The emitter branch of this 
transistor T.sub.32 is connected to a working resistor R.sub.32 as well as 
to a transistor T.sub.33 connected as a diode. The transistor T.sub.33 
together with the transistor T.sub.12 in the reference voltage circuit 11 
forms a current mirror, so that the same current designated with reference 
symbol I.sub.1 flows through these two branches. Connected in the 
collector branch of the transistor T.sub.32 is a transistor T.sub.31, the 
drive of which will be described in further detail below. 
A transistor T.sub.10 is addressed by the emitter of the transistor 
T.sub.32 of the output driver 13. The transistor T.sub.10, together with 
an emitter resistor R.sub.10, serves as a current source transistor for 
feeding a diagrammatically illustrated load 20. This load 20 can be 
formed, for instance, by an integrated circuit. 
It should be pointed out that several current-source transistors similar to 
the transistor T.sub.10 may be connected to the output of the driver 13 at 
the emitter of the transistor T.sub.32. Such transistors are driven in 
parallel by a current I.sub.L. The output d-c voltage U.sub.R which is 
independent of fluctuations of the supply voltage U.sub.O, is present at 
the resistor R.sub.10. In order to obtain a d-c output voltage U.sub.R 
which is independent over a wide range of the d-c supply voltage and the 
component parameters, the transistor T.sub.21 in the inverting amplifier 
12 is addressed through a resistor R.sub.21, and the transistor T.sub.31 
in the output driver 13, is addressed through a resistor R.sub.31 by the 
tap of the voltage stabilizing circuit, at which the prestabilized voltage 
U.sub.v is present. The coupling via the resistor R.sub.21 further 
improves the amplification in the direction toward a more accurate setting 
of the gain -1 of the inverting amplifier. 
The transistor T.sub.11 in the reference voltage circuit 11 is furthermore 
addressed through a resistor R.sub.B from the junction point of the 
transistors T.sub.31 and T.sub.32 in the output driver 13. 
The current flowing through the transistors T.sub.31 and T.sub.32 in the 
output driver 13 is designated with reference symbols I.sub.1 +I.sub.L. 
The current flowing through the transistor T.sub.22 in the inverting 
amplifier is further designated with reference symbol I.sub.2. The voltage 
U.sub.D is assumed to drop at the reference diode D.sub.11. 
For determining the d-c output voltage U.sub.R, the following two circuits 
or loops in the overall circuit will be considered in further detail. 
The first circuit extends from the tap of the voltage stabilizing circuit 
10 carrying the voltage U.sub.v through the resistor R.sub.21, the 
transistor T.sub.21, the resistor R.sub.22, the transistor T.sub.32, the 
transistor T.sub.10 and the resistor R.sub.10. 
The second circuit extends from the tap carrying the voltage U.sub.v 
through the resistor R.sub.31, the transistor T.sub.31, the resistor 
R.sub.B, the transistor T.sub.11, the diode D.sub.11, the transistor 
T.sub.22 and the resistor R.sub.23. 
Under the assumption that in accordance with the invention the resistors 
R.sub.21, R.sub.22, R.sub.23 and R.sub.31 have the same resistance value, 
the following equations are obtained for the two above-mentioned circuits 
if base currents of the second order are ignored: 
##EQU1## 
In these equations, the subscripts BE with a particular numeral refer to 
the base-emitter voltage of the corresponding transistors and .beta. 
refers to their current gain. 
If it is taken into consideration that the same voltage drop occurs across 
the base-emitter paths through which an equal current flows, the following 
is obtained from equations (1) and (2) 
EQU U.sub.R =U.sub.D +R.sub.B I.sub.1 /.beta. (3). 
It can be seen from the above equation (3) that the d-c output voltage 
U.sub.R is independent of the voltage U.sub.v and the current I.sub.L 
flowing through the load circuit, and it is therefore independent of the 
d-c supply voltage U.sub.O and the load 20. 
By means of the resistor R.sub.B, the current loss between the emitter and 
the collector current of the transistor T.sub.10 can be equalized if 
R.sub.B =R.sub.32. If R.sub.B =n.multidot.R.sub.32, the .alpha. factors of 
further n-1 transistors can be compensated corresponding to the transistor 
T.sub.10 in the active part of the circuit. 
The voltage drops occuring across the resistors of the active part of the 
circuit are proportional to the voltage U.sub.D. With the same 
proportionality factor, the temperature response of the diode D.sub.11 and 
the voltage U.sub.D, respectively, is also transmitted. This is desirable 
in many cases, because voltages at resistors and diodes thereby show the 
same temperature behavior, and therefore differential signals in the 
circuits are free of temperature influences. 
In some cases, however, a temperature response of the diodes is 
undesirable. 
In such cases, the diode D.sub.11 can be replaced by a circuit supplying a 
temperature-stable reference voltage, such as is known in principle from 
"IEEE Journal of Solid-State Circuits", SC-7 (1972), Pages 267 to 269. 
The foregoing is a description corresponding to German application No. P 31 
37 451.4, dated Sept. 21, 1981, the International priority of which is 
being claimed for the instant application, and which is hereby made part 
of this application. Any discrepancies between the foregoing specification 
and the aforementioned corresponding German application are to be resolved 
in favor of the latter.