AN6077 INTERSIL [Intersil Corporation], AN6077 Datasheet - Page 8

• Manufacturer Part Number: AN6077
• Description: An IC Operational Transconductance Amplifier With Power Capability
• Manufacturer: INTERSIL [Intersil Corporation]

Appendix A - V
The equivalent circuit for the V
Figure A1. The voltage E1 is given by:
The value of V
the transistor, which is, in turn, dependent on the input
current I since:
FIGURE A1. EQUIVALENT CIRCUIT FOR THE V
E
I
e
E
E
1
S
S
=
=
+
I
------------ -
R
–
+
1
V
--------- -
5 F
5 F
R
I
1
be
2
+
1 F
1 F
3.9K
3.9K
FIGURE 19. A CA3080 PREAMPLIFIER
V
be
be
I
1
is itself dependent on the emitter current of
0.002 F 680pF
56K
0.002 F 680pF
56K
+
1.5M
1.5M
2
3
2
3
-------------------------
R
be
2
V be
R
1
+
Multiplier
-
-
+
+
120K
120K
CA3080
CA3080
1
5
5
4-8
56K
56K
be
R
R
1
2
multiplier is shown in
7
4
7
4
5.6K
V+
V
5.6K
-
I
e
6
6
+
+
-
-
E
1
be
50 F
50 F
MULTIPLIER
Application Note 6077
(EQ. A1)
(EQ. A2)
E
E
OUT
OUT
The derivative of Equation A1 with respect to I yields the
incremental impedance of the V
dE
----------
where K
from:
V
Equation A4 is but another form of the diode equation:
I
Using the values shown in Figure 14, plus data on the
2N6292 (a typical transistor that could be used in the circuit),
the dynamic impedance of the circuit at a total current of
40mA is found to be 4.6 . In the actual design of the V
multiplier, the value of IR
transistor will never become forward biased.
Appendix B - Tone Controls
Figure B1 shows four operational amplifier circuit
configurations and the gain expressions for each. The
asymptotic low frequency gain is obtained by letting S
approach zero in each case:
Bass Boost: A
Bass Cut: A
Treble Boost: A
The asymptotic high-frequency gain is obtained by letting S
increase without limit in each expression:
Bass Boost: A
Bass Cut: A
Treble Boost: A
Treble Cut: A
Treble Cut: A
e
dI
be
1
=
=
=
I
S
K
e
Z
3
3
qV
-------------- - 1
=
lnI
KT
is a constant of the transistor Q
LOW
HIGH
be
------------ -
e
R
HIGH
LOW
+
LOW
HIGH
–
–
1
1
K
LOW
HIGH
2
=
+
=
=
=
R
---------------------------------- -
=
1
=
R
-------------------- -
1
=
C
-------------------- -
+
R
---------------------------------- -
1
=
R
C
---------------------------------- -
R
-------------------- -
R
+
1
1
+
-------------------------
2
C
-------------------- -
2
1
C
2
1
R
C
+
R
+
R
+
1
+
+
4
+
BR
+
2
C
1
2
2
C
R
R
2
+
R
-------------------- -
C
R
+
C
1
4
+
4
C
must be greater than V
2
2
3
C
1
2
1
1
R
C
1
+
R
4
+
C
3
2
C
-------------------- -
R
2
C
C
4
3
3
4
be
3
------------------------- -
R
+
C
2
C
K
multiplier:
4
I
4
3
e
R
+
2
K
3
1
and can be found
be
(EQ. A3)
(EQ. A4)
(EQ. A5)
or the
be