22
(2) Precaution for using the transistor output module
(a) Action against reverse current
If a transistor output module is wired as shown below, reverse current flows in an output element, causing a
failure of the element.
When wiring a transistor output module, connect a diode as shown below.
• When connecting transistor output modules in parallel
• When incorporating an additional circuit parallel to a transistor output module
(b) Measures against back EMF
When an inductive load is connected, connect a diode in parallel with the load.
Use a diode that meets the following conditions.
• Reverse breakdown voltage is equal to or more than 10 times as large as the circuit voltage.
• Forward current is equal to or more than 2 times as large as the load current.
OUT1
OUT2
COM
OUT1
OUT2
COM
Diode
Diode
Diode
Diode
Load
Load
Sink type
OUT1
OUT2
COM
OUT1
OUT2
COM
Diode
Diode
Diode
Diode
Load
Load
Source type
OUT
COM
Sink type
Additional circuit
Source type
Diode
OUT
COM
Diode
Additional circuit
Inductive
load
OUT
COM
Sink type
Diode
Inductive
load
OUT
COM
Source type
Diode