Operational amplifier designed to have increased output range

Details Operational amplifier designed to have increased output range Operational amplifier designed to have increased output range

2001-01-24

2002-08-13

Pascal, Robert (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including differential amplifier

C330S267000

Reexamination Certificate

active

06433636

ABSTRACT:

BACKGROUND OF THE INVENTION
1 Technical Field of the Invention
The present invention relates generally to an operational amplifier designed to have an increased output range.
2 Background Art
FIG. 4
shows an example of conventional operational amplifiers. The shown operational amplifier includes a differential amplifier
50
, an output circuit
60
, and a control circuit
70
. The differential amplifier
50
outputs a signal as a function of a potential difference between an input signal to a non-inverting input Tp (+input) and an input signal to an inverting input Tn (−input). The output circuit
60
is made of the so-called push-pull circuit including a pair of output transistors Tr
61
and Tr
62
. The control circuit
70
controls the output transistors Tr
61
and Tr
62
as a function of the output of the differential amplifier
50
and outputs a signal as a function the potential difference between the input signal to the non-inverting input Tp and the input signal to the inverting input Tn from an output terminal To connected to a junction of the output transistors Tr
61
and Tr
62
(i.e., emitters of the transistors Tr
61
and Tr
62
).
The differential amplifier
50
includes PNP transistors Tr
50
and Tr
51
. The PNP transistor Tr
50
connects at an emitter thereof with a power supply line Lv leading to a positive voltage terminal of a dc power supply (not shown) through a power supply terminal Tv and at a base thereof with a constant-current source (not shown) through a current control terminal Tc and outputs constant currents controlled by the constant-current source from three collectors thereof. Similarly, the PNP transistor Tr
51
connects at an emitter thereof with the power supply line Lv and at a base thereof with the constant-current source through the current control terminal Tc and outputs constant currents from by the constant-current source from two collectors thereof.
Each of the transistors Tr
50
and Tr
51
works as a constant-current source for the differential amplifier
50
. Specifically, the current outputted from each of the transistors Tr
50
and Tr
51
activates eight transistors Tr
52
to Tr
59
, as described later in detail, to output the signal as a function of the potential difference between the input signal to the non-inverting input Tp and the input signal to the inverting input Tn.
The transistor Tr
52
is a PNP transistor which connects at a base with the non-inverting input Tp, at an emitter with the first collector of the PNP transistor Tr
51
through a diode D
51
, and at a collector with a ground line Lg. The ground line Lg is supplied with the power from the dc power supply (not shown) along with the power supply line Lv and connects with a negative voltage terminal of the dc power supply through a ground terminal Tg. The diode D
51
connects at a cathode with the emitter of the PNP transistor Tr
52
and at an anode with the first collector of the PNP transistor Tr
51
.
The transistor Tr
53
is a PNP transistor which connects at a base with a junction of the anode of the diode D
51
and the first collector of the PNP transistor Tr
51
and at an emitter with the first collector of the PNP transistor Tr
50
.
The transistor Tr
54
is a PNP transistor which connects at a base with the inverting input Tn, at an emitter with the second collector of the PNP transistor Tr
51
through a diode D
52
, and at a collector with the ground line Lg. The diode D
52
connects at a cathode with the emitter of the PNP transistor Tr
54
and at an anode with the second collector of the PNP transistor T
51
.
The transistor Tr
55
is a PNP transistor which connects at a base with a junction of the anode of the diode D
52
and the second collector of the PNP transistor Tr
51
and at an emitter with the first collector of the PNP transistor Tr
50
along with the emitter of the PNP transistor Tr
53
.
The transistor Tr
56
is a PNP transistor which connects at an emitter with the second collector of the PNP transistor Tr
50
, at a base with the collector of the PNP transistor Tr
53
, and at a collector with the ground line Lg.
The transistor Tr
57
is a PNP transistor which connects at an emitter with the third collector of the PNP transistor Tr
50
, at a base with the collector of the PNP transistor Tr
55
, and at a collector with the ground line Lg.
The transistor Tr
58
is an NPN transistor which connects at a collector with the collector of the PNP transistor Tr
53
and the base of the PNP transistor Tr
56
at an emitter with the ground line Lg, and at a base with the collector thereof.
The transistor Tr
59
is an NPN transistor which connects at a collector with the collector of the PNP transistor Tr
55
and the base of the PNP transistor Tr
57
at an emitter with the ground line Lg, and at a base with the base of the PNP transistor Tr
58
to form a current mirror along with the NPN transistor Tr
58
.
The control circuit
70
also includes PNP transistors Tr
70
and Tr
71
and six transistors Tr
72
to Tr
77
activated by a supply of power from the transistors Tr
70
and Tr
71
. The PNP transistor Tr
70
connects at an emitter thereof with the power supply line Lv, and at a base thereof with the constant-current source through the current control terminal Tc and outputs constant currents from by the constant-current source from four collectors thereof. Similarly, the PNP transistor Tr
71
connects at an emitter thereof with the power supply line Lv and at a base thereof with the constant-current source through the current control terminal Tc and outputs constant currents from by the constant-current source from five collectors thereof.
The transistor Tr
72
is an NPN transistor which connects at a base with the emitter of the PNP transistor Tr
57
, at a collector with the first collector of the PNP transistor Tr
70
, and at an emitter with the ground line Lg through a resistor R
71
.
The transistor Tr
73
is an NPN transistor which connects at a base with the emitter of the NPN transistor Tr
72
, at an emitter with the ground line Lg, and at a collector with the base of the PNP transistor Tr
57
through a phase compensating capacitor C
71
, the bases of the output transistors Tr
61
and Tr
62
of the output circuit
60
, and the five collectors of the PNP transistor Tr
71
.
The transistor Tr
74
is an NPN transistor which connects at an emitter with the collector of the NPN transistor Tr
72
and the first collector of the PNP transistor Tr
70
, and at a collector with the ground line Lg, and at a base with the second to fourth collectors of the PNP transistor Tr
70
.
The transistor Tr
75
is an NPN transistor which connects at a collector with the base of the PNP transistor Tr
74
(i.e., the second to fourth collectors of the PNP transistor Tr
70
), at an emitter with the ground line Lg, and at a base with a collector thereof.
The transistor Tr
76
is an NPN transistor which connects at a collector with the output terminal To, at an emitter with the ground line Lg, and at a base with the base of the NPN transistor Tr
75
to form a current mirror along with the NPN transistor Tr
75
.
The transistor Tr
77
is an NPN transistor which connects at a collector with the five collectors of the PNP transistor Tr
71
(i.e., the bases of the output transistors Tr
61
and Tr
62
of the output circuit
60
and the collector of the NPN transistor Tr
76
), at an emitter with the collector of the NPN transistor Tr
76
(i.e., the output terminal To), at a base directly with the emitter of the output transistor Tr
61
and with the emitter of the output transistor Tr
62
through a resistor R
61
.
In the output circuit
60
, the output transistor Tr
61
connects at the collector with the power supply line Lv. The output transistor Tr
62
connects at the collector with the ground line Lg and at the emitter with the emitter of the output transistor Tr
61
through the resistor R
61
and with the output terminal To.
In operation, when the differential amplifier
50
receives the input signals to the non-inverting input Tp and the inverting input Tn through the PNP tr

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