Hi,
I am trying to build an amp capable of driving +/- 12 volts into a
50 ohm load over a range of frequencies from DC - ~100 mhz. As if that
wasn't hard enough, it needs to be about 2 cm^2 in size. Additionally
the output must be able to go into a high impedance state which
presents very little capacitance to the bus. I've gone through a lot
of different design ideas and have settled on this kind of weird
architecture. The schematic is here:
http://prymfg.com/schema.jpg
The output transistors are 2sk1403 and 2sc3597. The opamps are
actually ad8045's. Even with only one half of the push-pull, this
design isn't stable. At least according to spice it oscillates in the
5-65GHZ region. I'm not really sure if spice can be trusted at all.
How would a circuit like this be analyzed? Will it work or how can I
make it. I've tried things like using transconductance amplifiers,
using a mosfet as a second stage and adding feedback filters.
Thanks in advance.
Jon Pry
I am trying to build an amp capable of driving +/- 12 volts into a
50 ohm load over a range of frequencies from DC - ~100 mhz. As if that
wasn't hard enough, it needs to be about 2 cm^2 in size. Additionally
the output must be able to go into a high impedance state which
presents very little capacitance to the bus. I've gone through a lot
of different design ideas and have settled on this kind of weird
architecture. The schematic is here:
http://prymfg.com/schema.jpg
The output transistors are 2sk1403 and 2sc3597. The opamps are
actually ad8045's. Even with only one half of the push-pull, this
design isn't stable. At least according to spice it oscillates in the
5-65GHZ region. I'm not really sure if spice can be trusted at all.
How would a circuit like this be analyzed? Will it work or how can I
make it. I've tried things like using transconductance amplifiers,
using a mosfet as a second stage and adding feedback filters.
Thanks in advance.
Jon Pry