How to convert TTL signals into bipolar signals ?

[matrix1]

WaveShaping

i want to convert TTL (or LVTTL) signals into bipolar signals of about ±5V or closer to it as much possible. and also decrease the slew rate of the wave so as to look like a trapezoidal waveorm ( typ. 200 ns rise/fall times). my limitation is +5V supply voltage, and i have to use voltage inverter ICs to get -5V.
how could i do this using minimal component count. i woulld like to use mosfet, BJT
or OPAMPs to perform the task.
also how could i calculate the output impedance of the circuit.
please guide me ...Thanx

 

[IanP]

Re: WaveShaping

One way of performing thes conversion is to us an opamp, connect TTL signal to (+) input and a reference voltage of, say, 2V to (-) input. This opamp has to be supplied of +/-%V so its input will be +%V if the input volage has TTL level H and -5V if the (+) input has TTL level L.
To slow down the rising and falling edges you can use a resistor (for example 100Ω) in series with the opamp output and a small capaictor the other sideo of resistor and 0V (LPF).
As the output impedance of an ideal opamp is ≈0Ω (in practice this will be a couple of Ωs) so your output impedance will be this 100Ω resistor connected in parallel with that small capacitor ..

 

[matrix1]

Re: WaveShaping

As far as bipolar conversion is concerned that may be OK (OPAMP's SR is also critical for such operation..any good suggestion or part no) but if i use LPF then the
signal may be distorted and linearity could not be maintained and also rise and fall time difference is usually seen...secondly could this all be applied to a wave having
variable or continuously changing duty cycle because it makes function even worse.
Also i need a maximum of 500mA of current per channel ( there are two waves inverted to each other). And i receive and transmit on the same line so how could i
disconnect from the line and again connect when i need to....thanx.