rmanor
Newbie level 3
current mirror
Hi,
When I look at the an NPN current mirror (implemented with BJTs), I understand why the diode connection (base and collector are short circuted) is required at the master transistor - we need to copy the voltage at the collector to the base in order to have the Vbe voltage in the active mode (usually > 0.7V).
But in the PNP current mirror, as far as I can see), even if I don't do the diode connection there is a sufficient Vbe voltage ( < -0.7 for PNP).
Where am I wrong? or is the connection there for a different reason?
thanks.
Hi,
When I look at the an NPN current mirror (implemented with BJTs), I understand why the diode connection (base and collector are short circuted) is required at the master transistor - we need to copy the voltage at the collector to the base in order to have the Vbe voltage in the active mode (usually > 0.7V).
But in the PNP current mirror, as far as I can see), even if I don't do the diode connection there is a sufficient Vbe voltage ( < -0.7 for PNP).
Where am I wrong? or is the connection there for a different reason?
thanks.