Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

MCP616 Datasheet(PDF) 18 Page - Microchip Technology

Part No. MCP616
Description  2.3V to 5.5V Micropower Bi-CMOS Op Amps
Download  38 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  MICROCHIP [Microchip Technology]
Homepage  http://www.microchip.com
Logo 

MCP616 Datasheet(HTML) 18 Page - Microchip Technology

Zoom Inzoom in Zoom Outzoom out
 18 / 38 page
background image
MCP616/7/8/9
DS21613C-page 18
© 2008 Microchip Technology Inc.
4.8
PCB Surface Leakage
In applications where low input bias current is critical,
Printed Circuit Board (PCB) surface leakage effects
need to be considered. Surface leakage is caused by
humidity, dust or other contamination on the board.
Under low humidity conditions, a typical resistance
between nearby traces is 1012
Ω. A 5V difference would
cause 5 pA of current to flow, which is greater than the
MCP616/7/8/9
family’s
bias
current
at
25°C
(1 pA, typical).
The easiest way to reduce surface leakage is to use a
guard ring around sensitive pins (or traces). The guard
ring is biased at the same voltage as the sensitive pin.
An example is shown below in Figure 4-8.
FIGURE 4-8:
Example Guard Ring Layout
for Inverting Gain.
1.
Non-inverting Gain and Unity Gain Buffer:
a) Connect the non-inverting pin (VIN+) to the
input with a wire that does not touch the
PCB surface.
b) Connect the guard ring to the inverting input
pin (VIN–). This biases the guard ring to the
common mode input voltage.
2.
Inverting Gain and Transimpedance gain (con-
vert current to voltage, such as photo detectors)
amplifiers:
a) Connect the guard ring to the non-inverting
input pin (VIN+). This biases the guard ring
to the same reference voltage as the op
amp (e.g., VDD/2 or ground).
b) Connect the inverting pin (VIN–) to the input
with a wire that does not touch the PCB
surface.
4.9
Application Circuits
4.9.1
HIGH GAIN PRE-AMPLIFIER
The MCP616/7/8/9 op amps are well suited to
amplifying small signals produced by low-impedance
sources/sensors. The low offset voltage, low offset
current and low noise fit well in this role. Figure 4-9
shows a typical pre-amplifier connected to a low-
impedance source (VS and RS).
FIGURE 4-9:
High Gain Pre-amplifier.
For the best noise and offset performance, the source
resistance RS needs to be less than 15 kΩ. The DC
resistances at the inputs are equal to minimize the
offset voltage caused by the input bias currents
(Section 4.2 “DC Offsets”). In this circuit, the DC gain
is 10 V/V, which will give a typical bandwidth of 19 kHz.
4.9.2
TWO OP AMP INSTRUMENTATION
AMPLIFIER
The two-op amp instrumentation amplifier shown in
Figure 4-10 serves the function of taking the difference
of two input voltages, level-shifting it and gaining it to
the output. This configuration is best suited for higher
gains (i.e., gain > 3 V/V). The reference voltage (VREF)
is typically at mid-supply (VDD/2) in a single-supply
environment.
FIGURE 4-10:
Two-Op Amp
Instrumentation Amplifier.
The key specifications that make the MCP616/7/8/9
family appropriate for this application circuit are low
input bias current, low offset voltage and high common-
mode rejection.
Guard Ring
VIN–VIN+ VSS
MCP616
RF
RG
11.0 k
Ω
100 k
Ω
RS
10 k
Ω
VDD/2
VS
VOUT
V
OUT
V
1
V
2
() 1
R
1
R
2
------
2R
1
R
G
----------
++
⎝⎠
⎜⎟
⎛⎞
V
REF
+
=
R2
R1
MCP617
VOUT
V2
VREF
½
R1
R2
V1
RG
MCP617
½


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38 


Datasheet Download




Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn