Biomedical Engineering Reference
In-Depth Information
+15V
+5V
+15V
IC4D
CD40106B
14
LED2
R38
10
9
8
OVERLOAD
INDICATOR
C12
2
2
uF
+15V
+
7
R39
1.5K
-15V
+15V
DISP1
TSM39168
IC7A
TL074
11
IC4E
CD 40106B
14
D19
4
10
1 12
+15V
2
-
+
8
1
11
10
3
6
Display1
1N4148
Display_In
7
9
R34
1K
R3 6
10K
C13
100nF
4
R38
1M
+15V
3
5
+15V
R37
2K
R35
121
14
IC4F
CD 40106B
13
12
7
IC8
+15V
L78M08/TO220
1
2
VIN
VOUT
+8V
J1
+5V
C23
10nF
C15
100uF
+
C16
10nF
1
2
3
4
6
7
8
9
10
C17
C18
3
10nF
470nF
C21
C22
C19
100uF
+
C20
10nF
10nF
470nF
1
3
2
VIN
VOUT
-8V
IC9
L7908/TO220
-15V
Figure 2.39
Signal levels are indicated by a TSM39168 VU LED bar graph display. The transition from the green LEDs to the orange
LEDs occurs at 1 V. The tenth LED (red) is activated when the voltage reaches 1.5 V. LED2 indicates that the output level is too high.
A voltage of
15 V power for the filter unit is supplied via connector J1. IC8 and IC9 are low-power
8-V regulators to supply the analog
transmission gate (IC2) and the quad NAND gate (IC5). The
5-V power for the bar graph display has a separate input.
er that imple-
ments a similar transient-elimination technique to enable detection of evoked-response
events from the heart soon after the delivery of pacing or de
More recently, André designed an intracardiac electrogram signal ampli
fi
fi
brillation pulses. The ampli-
fi
fier of Figure 2.40 receives a digital BLANK command just before (e.g., 1 ms) the tran-
sient event (e.g., a pacing or de
brillation pulse) is delivered to the heart. Under normal
conditions, the electrogram signal detected via intracardiac electrodes (from pacing leads
or a mapping catheter) is presented to an INA128 instrumentation ampli
fi
er (IC3) via ac-
coupling capacitors C3 and C6. Resistors R4 and R8, together with C5 and C7, low-pass
the input signals. The output of the instrumentation ampli
fi
fi
er is
fi
filtered by the second-
order Butterworth high-pass
filter built around IC1B.
When a BLANK signal is delivered to the biopotential ampli
fi
fi
er circuit, the inputs of
the instrumentation ampli
fi
er are shorted to the analog signal ground via analog switches
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