Further study of Y-matrix and Z-matrix configuration has led to development of efficient, dependable high-quality gyrators. Efficiency of new gyrators may approach theoretical limit of 78.5% with further improvements. Both designs are comparatively easy to integrate by implementing technology used with conventional operational amplifiers

Hochmair, E. S.

English

NASA Technical Reports Server

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May 1973	 B73-10159 
NASA TECH BRIEF 
•	 Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Integrable Power Gyrator 
Current/Voltage	 I 
Converter
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Complementar 
	
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2	 I1_54[__ Output Stage 
Output 
	
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Simplified Circuit Diagram Of The Noninverting VCCS 
.
The problem 
Gyrators have been in existence for some time now. 
Synthesis of gyrators by different methods such as a 
voltage-controlled current-source (VCCS) approach, de-
composition of the Z-matrix, approaches using oper-
ational amplifiers, etc., has produced gyrators having 
very low efficiency on the order of 1%. The result has 
been that these gyrators cannot handle signals above 
several milliwatts without excessive dissipation of dc 
power.
The solution: 
A further study of the Y-matrix (VCCS approach) 
and the Z-matrix configuration has led to development 
of efficient, dependable high-quality gyrators. 
How it's done: 
The basic configuration used for the Y-matrix gyrator 
comprises two essentially similar VCCS's in a loop with 
one producing a 1800 phase reversal and the other 
producing zero phase change. This circuit is reciprocal, 
and the input signal may drive either the amplifier with 
phase reversal or the one without.
(continued overleaf) 
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The basic circuit of the nonrnverting VCCS is shown 
in the figure. It consists of the differential amplifier, the 
complementary output stage, and the current/voltage 
converter connected in a feedback loop. The current/ 
voltage converter performs the same function as the 
ordinary gyration resistor in conventional gyrators: it 
produces a voltage that is proportional to the output 
current. This voltage is fed back to the differential 
amplifier. This type of feedback is called current 
proportional voltage feedback which stabilizes the VCCS 
transconductance and, at the same time, enhances the 
output resistance of the output stage and the input 
resistance of the differential amplifier. The configura-
tion provides stable transconductance and high input 
and output resistances which are all necessary for a high 
quality Y-matrix gyrator. 
In general, high efficiency of the circuit is provided 
by the following: 
1. Class B output stage 
2. Small current flow through gyration resistors R 1 and 
R4 as compared with the output current 
3. Current flow through the differential amplifier and 
of the transistors Q 1 and Q2 is small compared to the 
output current. 
Performance of this current with a 10-V supply 
voltage may be summarized as follows: 
1. Voltage amplification factor = 600 
2. Transconductance = 1.8 millisiemens 
3. Output resistance = 300 kilohms 
4. Input resistance output resistance 
5. Efficiency = 38%. 
The inverting VCCS is essentially similar to the 
nomnverting one. However, to invert the phase, the 
inputs of the differential amplifier have to be inter-
changed. Since the feedback has to stay negative, 
further phase reversal in the feedback path is necessary. 
This is accomplished by insertion of another differential 
amplifier connected as an inverter (amplification factor 
= —1). Because the efficiency of the inverting VCCS is 
also 38%, efficiency of the complete circuit is 19% - a 
significant improvement over the previous 1%. 
The Z-matrix gyrator incorporates the same basic 
building blocks of the Y-matrix type but combines them 
in a different way. As in the case of the Y-gyrator, the
output of each differential amplifier is connected to a 
complementary output stage which in turn is connected 
to a current/voltage converter. The current/voltage 
converter produces a voltage that is proportional to the 
current flowing into the corresponding port (input or out-
put) of the gyrator (see figure). This voltage, however, is 
not fed back to the differential amplifier, but drives either 
directly or by insertion of an inverter (voltage gain = —1). 
to the noninverting input of the other differential am-
plifier. In order to ensure a low output resistance and a 
high input resistance, the output voltage at each port of 
the gyrator is fed back to the inverting input of the 
corresponding differential amplifier. 
Results from either approach have been favorable. 
With further improvements in design details, efficiency 
of the new gyrators may now approach the theoretical 
limit of 78.5%. This will allow handling of signals of 
considerable power with moderate dc power dissipation. 
Improvements in quality factor Q have reached 300 for 
Y-matrix and 1300 for Z-matrix gyrators. Finally, both 
designs are comparatively easy to integrate by imple-
menting the same technology as used with conventional 
operational amplifiers. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Reference: B73-10159 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Source: E. Hochmair of 
National Academy of Sciences 
under contract to
Marshall Space Flight Center 
(MFS-22342)
. 
B73-10159	 Category 02	 0


Integrable power gyrator

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