120 GBd 2.8 Vpp,diff Low-Power Differential Driver for InP Mach–Zehnder Modulator Using 55-nm SiGe HBTs

We present a 120 GBd
$2.8 V_{\mathrm {pp,diff}}$
driver for InP Mach–Zehnder modulator (MZM) using 55-nm SiGe heterojunction bipolar transistor (HBTs). The output impedance of the driver has a differential
$2\times 25\,\,\Omega $
, matched to the optical modulator. The measured 3-dB bandwidth exceeds 67 GHz, and the output
$P_{\mathrm {1\,dB}}$
is about 16.7 dBm at 1 GHz. The variable gain using the Gilbert-cell is implemented, and a 2.1 dB gain variation is measured. The total harmonic distortion (THD) is 2.5% at 1 GHz. The power consumption is 960 mW. The eye openings up to 120 GBd are characterized by exploiting the impedance conversion integrated circuit (IC), which is de-embedded afterward. The post-processing of the de-embedding results in the rail-to-rail voltage output of
$2.8 V_{\mathrm {pp,diff}}$
.