We report a technique for generation of ultra-broadband coherent femtosecond continua in the infrared. The laser architecture is based on the Cr:ZnS–GaSe and Cr:ZnS–ZGP tandem arrangements that enable simultaneous amplification of ultrashort middle IR pulses and augmentation of pulses’ spectrum via a chain of intrapulse three-wave mixings. The first part of the tandems is based on a single-pass polycrystalline Cr:ZnS amplifier, which is optically pumped by off-the-shelf continuous wave Er-doped fiber laser and outputs 2-cycle pulses with multi-Watt average power at 80 MHz repetition rate, at the central wavelength 2.5 μm. The second stage of the tandems comprises a GaSe or ZGP crystals configured for intrapulse difference frequency generation. The Cr:ZnS–GaSe tandem has allowed us to achieve multi-octave 2–20 μm continuum with 2 W power in the range 2–3 μm and power in excess of 20 mW in the important range 3–20 μm. On the other hand, Cr:ZnS–ZGP tandem features long-wave infrared (6–12 μm) output pulses with record braking sub-Watt power level. Last but not least, Cr:ZnS–GaSe and Cr:ZnS–ZGP IR sources have small footprints and are easily convertible to the optical frequency combs with low carrier-to-envelope timing jitter.