RC4200 View Datasheet(PDF) - Fairchild Semiconductor
Part Name
Description
Manufacturer
RC4200 Datasheet PDF : 23 Pages
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PRODUCT SPECIFICATION
RC4200
Voltage Multiplier/Divider
R1
8
VX
I1
7
R4
5
VZ
I4
RC4200
VY
R2
1
I2
4
2
3
I3
6
RO VO
VXVY = VOVZ
–VS
R1R2 ROR4
65-4200-04
Figure 3. Voltage Multiplier/Divider
Solving for V0
=
V-----X----V----Y------------R----0---R----4-
VZ
R1R2
For a multiplier circuit VZ = VR = cons tan t
Therefore: V0
=
VXVYK where K
=
-----R----0---R----4-----
VRR1R2
For a divider circuit VY = VR = cons tan t
Therefore: V0
=
V-----X-- K
VZ
where K
=
V-----R----R----0---R----4-
R1R2
Extended Range
The input and output voltage ranges can be extended to
include 0 and negative voltage signals by adding bias
currents. The RSCS filter circuits are eliminated when the
input and biasing resistors are selected to limit the respective
currents to 50 µA min. and 250 µA max.
Extended Range Multiplier
VX
(Input)
VY
(Input)
RA
R1
R2
RB
RC
8
5
I1
I4
7
RC4200
1
I2
2
3
4
I3
6
RC4
–VS
+VREF
RD
VO
RO (Output)
+VS
RCX
–VS
65-4200-05
Figure 4. Extended Range Multiplier
Resistors Ra and Rb extend the range of the VX and VY
inputs by picking values such that:
I 1 ( min. )
=
V-----X----(--m-----i--n---.--) + V-----R----E---F-
R1
Ra
=
50 µA,
and I1(max.)
=
V-----X----(--m-----a--x---.--) + -V----R----E---F-
R1
Ra
=
250 µA,
also I2(min.)
=
V-----Y----(--m-----i-n---.--) + V-----R----E---F-
R2
Rb
=
50 µA,
and I2(max.)
=
V-----Y----(--m-----a--x---.--) + -V----R----E---F-
R2
Rb
=
250 µA.
Resistor RC supplies bias current for I3 which allows the
output to go negative.
Resistors RCX and RCY permit equation (6) to balance, ie.:
V-----X---
R1
+
V-----RR-----Ea----F-
V-----Y---
R2
+
V-----RR----b-E----F-
=
V-----0-
R0
+
-V----R-----E----F-
RC
+
---V----X-----
RCX
+
R---V--C--Y--Y---
V----R-R----D-E----F-
V-----Y-----V----X--- + V-----X-----V----R-----E----F-- + V-----Y-----V----R-----E----F-- + V-----R-----E----F- =
R1R2 R1Rb
R2Ra RaRb
V-----0----V----R-----E----F- + -V----X-----V----R-----E----F-- + V-----Y-----V----R-----E----F-- + V-----R-----E----F--2
R0Rd
RcxRd RCYRd RcRd
Cross-Product Cancellation
Cross-products are a result of ths VXVR and VYVR terms.
To the extend that R1Rb = RCXRD, and R2Ra = RCYRd
cross-product cancellation will occur.
Arithmetic Offset Cancellation
The offset caused by the VREF2 term will cancel to the
extent that RaRb = R0Rd, and the result is:
V-----Y----V----X--
R1R2
=
-V----0---V----R----E---F-
R0Rd
or
V0
=
VXVYK
where K = --------R----0---R----d--------
VREFR1R2
Resistor Values
Inputs:
VX(min.) ≤ VX ≤ VX(max.)
∆VX = VX(max.) – VX(min.)
VY(min.) ≤ VY ≤ VY(max.)
∆VY = VY(max.) = VY(min.)
VREF = Constant (+7V to +18V)
K = -----V-----0----- (Design Requirements)
VXVY
REV. 1.2.1 6/14/01
5
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