stable about load is inductor ???

[mickey0908]

hi everyone,
in my designing , the phase margin is about 60 degree. in our test, add a resistor as load, the ouput current is stable, add a inductor (voil coli motor) as a load, the output current is oscillation.
could you give me some suggestions about this circuit?

 

[renwl]

I think the phase margin is not 60 degree when a inductor (voil coli motor) as a load.

 

[chenjia]

1.the load(inductor) is not in the feedback loop;
2.The reason that there is unstable in some feedback network is due to inductor of the output impedance of amp(the avtive inductor, that amlifier can change the 'capacitor' to be 'inductor')
3.there is resonance frequency and ring in LC network in open loop topology

 

[mickey0908]

hi chenjia,

in my test.
1.use the same inductor, if use a resistor parallel connection with inductor, the output is stable(reduce the resistor). if not, the output is unsatble.
2. load is resistor, the value of resistor did not affect the output current, it is always stable.