Dc amplifiers in which all stages are dc-coupled (H 03 F 3/45
takes precedence) [3]
3
/
343
•
•
with semiconductor devices only [2]
3
/
345
•
•
•
with field-effect devices (H 03 F 3/347 takes precedence) [2]
3
/
347
•
•
•
in integrated circuits [2]
3
/
36
•
•
with tubes only
3
/
38
•
Dc amplifiers with modulator at input and demodulator at output; Modulators or demodulators specially adapted for use in such amplifiers (modulators in general H 03 C; demodulators in general H 03 D; amplitude modulation of pulses in general
H 03 K 7/02; amplitude demodulation of pulses in general H 03 K 9/02)
3
/
387
•
•
with semiconductor devices only [2]
3
/
393
•
•
•
with field-effect devices [2]
3
/
40
•
•
with tubes only
3
/
42
•
Amplifiers with two or more amplifying elements having their dc paths in series with the load, the control electrode of each element being excited by at least part of the input signal, e.g. so-called totem-pole amplifiers
3
/
44
•
•
with tubes only
3
/
45
•
Differential amplifiers [2]
3
/
46
•
Reflex amplifiers
3
/
48
•
•
with tubes only
3
/
50
•
Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower
3
/
52
•
•
with tubes only
3
/
54
•
Amplifiers using transit-time effect in tubes or semiconductor devices (parametric amplifiers H 03 F 7/00
; solid state travelling-wave devices H 01 L 45/02)
3
/
55
•
•
with semiconductor devices only [2]
3
/
56
•
•
using klystrons
3
/
58
•
•
using travelling-wave tubes
3
/
60
•
Amplifiers in which coupling networks have distributed constants, e.g. with waveguide resonators (H 03 F 3/54 takes precedence)
3
/
62
•
Two-way amplifiers
3
/
64
•
•
with tubes only
3
/
66
•
Amplifiers simultaneously generating oscillations of one frequency and amplifying signals of another frequency
3
/
68
•
Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
3
/
70
•
Charge amplifiers [2]
3
/
72
•
Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal [2]
5
/
00
Amplifiers with both discharge tubes and semiconductor devices as amplifying elements
7
/
00
Parametric amplifiers (devices or arrangements for the parametric generation or amplification of light, infra-red or ultra-violet waves G 02 F 1/39)
7
/
02
•
using variable-inductance element; using variable-permeability element
7
/
04
•
using variable-capacitance element; using variable-permittivity element
7
/
06
•
with electron beam tube
9
/
00
Magnetic amplifiers
9
/
02
•
current-controlled, i.e. the load current flowing in both directions through a main coil [2]
9
/
04
•
voltage-controlled, i.e. the load current flowing in only one direction through a main coil, e.g. Logan circuits (H 03 F 9/06 takes precedence) [2]
9
/
06
•
Control by voltage time integral, i.e. the load current flowing in only one direction through a main coil, whereby the main coil winding also can be used as a control winding, e.g. Ramey circuits [2]
11
/
00
Dielectric amplifiers
13
/
00
Amplifiers using amplifying element consisting of two mechanically- or acoustically-coupled transducers, e.g. telephone-microphone amplifier
15
/
00
Amplifiers using galvano-magnetic effects not involving mechanical movement, e.g. using Hall effect
17
/
00
Amplifiers using electroluminescent element or photocell
